Control of Congress has become so precariously balanced between the two parties that it may now be subject to the butterfly effect.
The butterfly effect is a mathematical concept, often applied to weather forecasting, that posits even seemingly tiny changes -- like a butterfly flapping its wings -- can trigger a chain of events that produces huge impacts.
Because it has become so difficult for either party to amass anything other than very narrow majorities in the House and Senate, the exercise of power in both chambers now appears equally vulnerable to seemingly miniscule shifts in the political landscape.
Just in the past few weeks, a revolt by a small band of House conservatives effectively denied the Republican majority control of the floor for days. At the same time, a Supreme Court voting rights decision that might affect only a handful of House seats has raised Democratic hopes of recapturing the chamber in 2024. In the Senate, the extended absence of a single senator to illness -- California Democrat Dianne Feinstein -- prompted an eruption of concern among party activists over the upper chamber's ability to confirm President Joe Biden's judicial nominations.
In different ways, these developments are all manifestations of the same underlying dynamic: the inability of either side to establish large or lasting congressional majorities.
Viewed over the long-term, majorities in the House and Senate for the past 30 years have consistently been smaller than they were when Democrats dominated both institutions in the long shadow of the New Deal from the 1930s into the 1980s. And those majorities have grown especially tight since former President Donald Trump emerged as the polarizing focal point -- pro and con --of American politics.
Since the Civil War, only rarely has either chamber been as closely divided between the parties as it is this year, with Republicans holding just a five-seat advantage in the House and Democrats clinging to a one-seat Senate majority. It's been even more rare for both chambers to be so closely divided at the same time -- and rarer still for them to be split almost evenly between the parties in consecutive Congresses, as they have been since 2021.
It remains possible that either side could break out to a more comfortable advantage in either chamber. The 2024 map offers Republicans an opportunity, especially if they run well in the presidential race, to establish what could prove a somewhat durable Senate majority. But many analysts consider it more likely that the House and Senate alike will remain on a razor's edge, with narrow majorities that frequently flip between the two sides.
The key development shaping this "butterfly effect" era are the indications that narrow majorities are now becoming the rule in both legislative chambers.
Slim majorities and frequent shifts in control have been a central characteristic of the Senate for longer. In the 12 Congressional sessions since 2001, one party or the other has reached 55 Senate seats only three times: Republicans after George W. Bush's reelection in 2004, and Democrats after Barack Obama's wins in 2008 and 2012. In six of the past 12 sessions, the majority party has held 52 Senate seats or less, including two when voters returned a Senate divided exactly 50-50.
By contrast, one party or the other amassed 55 seats or more seven times in the 10 sessions from 1981 through 2000. Lopsided majorities were even more common in the two decades of unbroken Democratic Senate control from 1961 to 1980: the party held at least 55 seats nine times over that interval.
Largely because the Senate majorities have been so small for the past several decades, control of the body has shifted between the parties more frequently than in most of American history. Neither party, in fact, has controlled the Senate for more than eight consecutive years since 1980. Never before in US history has the Senate gone so long without one party controlling it for more than eight years.
Generally, over the past few decades, the parties have managed somewhat more breathing room in the House. Neither side lately has consistently reached the heights that Democrats did while they held unbroken control of the lower chamber from 1955 through 1994 when the party routinely won 250 seats or more. But Republicans reached 247 seats after the second mid-term of Obama's presidency in 2014. Democrats, for their part, soared to more than 250 seats after Obama's victory in 2008, and 235 following the backlash against Trump in the 2018 election.
But the Democratic majority fell to just 222 seats after the 2020 election. And Republicans likewise eked out only 222 seats last fall, far below the party's expectations of sweeping gains. Those slim majorities may reflect a precarious new equilibrium. "I don't think a major swing in either direction is possible in this new normal," said Ken Spain, former communications director for the National Republican Congressional Committee. "We are in this perpetual state of power shifting hands, where the House is often times on a razor's edge."
Former Rep. Steve Israel, who served as chair of the Democratic Congressional Campaign Committee, sees the same pattern continuing. "We're looking at very narrow House majorities for the foreseeable future," he told me in an email.
Like the Senate, smaller majorities in the House are translating into more frequent shifts in control. While Democrats held the House for 40 consecutive years until 1994, the longest either party has controlled it since was the GOP majority from 1995 through 2006. In the post-1994 era, Democrats have twice captured the House only to lose it just four years later. If Republicans lose the White House next year, there is a strong chance they could surrender their current House majority after just two years.
As recent events show, this era of narrow majorities is changing how Congress operates in ways that are often overlooked in the day-to-day scrimmaging.
One is creating a virtually endless cycle of trench warfare over House redistricting. As I've written, the district lines for an unusually large number of seats are still in flux beyond the first election following the reapportionment and redistricting of seats after the decennial Census.
Because the margins in the House are now so small, the parties have enormous incentive to use every possible legal and political tool to influence any seat that could conceivably tip the balance. "We are in the perpetual redistricting era," said Marina Jenkins, executive director of the National Democratic Redistricting Committee. "We've been creeping into that era for the past 10 years, and I think it's just going to continue to be that way."
The two sides are scrimmaging across a broad battlefield. Republican gains on the state Supreme Courts in Ohio and North Carolina could pave the way for the GOP to draw new lines that might net the party a combined half a dozen House seats. Democratic gains on the state Supreme Courts in Wisconsin and New York could allow Democrats to offset that with new maps that produce gains of two seats in the former and four or five in the latter.
The Supreme Court's surprising decision this month to strike down Alabama's congressional map as a violation of the Voting Rights Act, could lead by 2024 to the creation of new Black-majority seats that would favor Democrats not only in Alabama, but also Louisiana and maybe Georgia, experts say. The Court's decision could also invigorate a voting rights case that could force Texas Republicans to create more Latino-majority seats there; while that case is unlikely to be completed in time for the 2024 election, it could ultimately produce a dramatic impact, with three or more redrawn seats that could favor Democrats. Racial discrimination cases brought on other grounds could eventually threaten GOP congressional maps in South Carolina, Arkansas and Florida.
And even all this maneuvering doesn't mark the end of the potential combat. If Democrats win multiple voting rights judgements against Republican-drawn maps, some observers think other GOP-controlled states may try to offset those gains by simply redrawing their own maps to squeeze out greater partisan advantage. Most states do not bar that sort of mid-decade redistricting, which was used most dramatically in Texas after the GOP won control of the state legislature there in 2002. "That threat is real," said Jenkins.
The unusual recent rebellion by House conservatives that denied the GOP a majority to control the floor marks another key characteristic of the butterfly effect era in Congress: the ability of small groups to exert disproportionate influence. When Democrats held their slim majority in the last Congress, they were stalemated for months by a standoff between centrists and progressives over whether to decouple the bipartisan infrastructure bill from Biden's sweeping Build Back Better agenda.
Ultimately, though, progressives reluctantly agreed to separate the two issues, allowing the infrastructure bill to pass. And then progressives, reluctantly again, agreed to pass the much scaled-back version of the Biden agenda that became the Inflation Reduction Act. Democrats, in fact, over the previous Congress displayed a record-level of party unity in passing not only those two bills but almost every other major party priority through the House, from multiple voting rights bills, to legislation restoring abortion rights nationwide, an assault weapon ban, police reform, and a bill barring LGBTQ discrimination.
Republican leaders are finding it tougher to corral their narrow majority. The recent backlash against the debt ceiling deal by far-right conservatives prevented Republicans from passing the "rules" needed to control floor debate on legislation in the House. Less than a dozen House Republicans joined the rebellion, but it was enough to trigger a stunning stumble into chaos for the majority party.
"Culturally the two parties are somewhat different when it comes to governing," said Spain, now a Washington-based communications consultant. "On the Democratic side there tend to be family squabbles but ultimately everybody falls in line... On the Republican side, the tail tends to wag the dog. I think [Speaker Kevin] McCarthy did a pretty effective job threading the needle in getting the debt ceiling negotiated. Now we're seeing the fall out."
Former Republican Rep. Charlie Dent, who now directs the Aspen Institute Congressional program, also believes it is more difficult for Republicans than Democrats to govern with a narrow House majority, largely because governing is not a priority for the right flank in the GOP conference.
"It's important to remember that the House Democratic conference certainly believes in governance," Dent said. "That's true of virtually all of them, whether they are more moderate or centrist vs. those who are on the far left. They want the government to function." But, he added, "When you have a narrow Republican majority like we do, there is a rump group in the House Republican caucus who simply thrives on throwing sand into the gears of government and don't want it to function well, if at all. They are more inclined to shut the government down. Some of them would be willing to default. And that's the difference" between the parties.
Narrow majorities are also roiling the Senate, as demonstrated both by the uproar over Feinstein's absence and the liberal discontent in the last Congress over the enormous influence of West Virginia Sen. Joe Manchin and Arizona Sen. Kyrsten Sinema. If Senate majorities stay as small as they have been recently, pressure is almost certain to grow for either party to end the filibuster the next time it wins unified control of the White House and Congress.
In this century, neither side has controlled the 60 Senate seats required to break a filibuster except for a few months when Democrats did in 2009 and early 2010 (until losing that super-majority when Republicans won a special election to replace Sen. Edward M. Kennedy, who had died of brain cancer.) And even as it has grown more difficult for either party to approach 60 Senate votes, both have also found it harder to attract more than token crossover support from senators in the other party. In a world where 60 Senate votes is virtually out of reach, it's difficult to imagine a party holding "trifecta" control of the White House and both congressional chambers granting the minority party a perpetual veto of the majority's agenda through the filibuster.
Political analysts caution that it remains possible that either party might break through this trench warfare to reestablish larger majorities. But to do so, it would need to overcome the interplay between two powerful political trends.
The first is the hardening separation of the country into reliably red and blue blocks. Far fewer states than in the past are genuinely up for grabs in the presidential race: perhaps as few as five to seven, or even less, may be truly within reach for both sides next year. And even within the states, the divisions are hardening between Democratic dominance in larger metropolitan areas and Republican strength outside of them.
The impact of this sorting both between and within the states is magnified by the second big trend: the decline of split-ticket voting. Fewer voters are hopscotching between the two sides with their votes; more appear to be viewing elections less as a choice between two individuals than as a referendum on which party they want in control of government.
In 2022, only 23 House Members were elected in districts that supported the other side's presidential candidate. (Eighteen House Republicans hold districts that voted Biden; just five House Democrats hold seats that voted for Trump.) Democrats now hold 48 of the 50 Senate seats in the 25 states that backed Biden in 2020 while Republicans hold 47 of the 50 in the 25 states that voted for Trump. And all three of those remaining Trump-state Democratic senators -- Ohio's Sherrod Brown, Montana's Jon Tester and West Virginia's Manchin -- face difficult reelection races in 2024.
With more states reliably leaning toward either party in the presidential race, and fewer legislators winning in places that usually vote the other way for president, both parties are grappling over a shrinking list of genuine congressional targets. Kyle Kondik, managing editor of Sabato's Crystal Ball, a political newsletter from the University of Virginia's Center for Politics, points out that wave elections that produce big congressional majorities typically have come when one party faces a bad environment and must also defend a large number of seats that it had previously won in places that usually vote for the other side. (That was the compound dynamic that wiped out rural House Democrats in 2010 and suburban House Republicans in 2018.) Now, he notes, the potential impact of a bad environment is limited because each side holds so few seats on the other's usual terrain. "Neither side is that dramatically overextended," said Kondik. "Everything is sorted out."
The paradoxical impact of more sorting and stability in the electorate, though, has been more instability in Congress, as the two sides trade narrow and fragile majorities. For the foreseeable future, control of Congress may pivot on the few quirky House and Senate races in each election that defy the usual partisan patterns. Such races are often decided by idiosyncratic local developments -- a scandal, a candidate with an unusually compelling (or repelling) personal style, a major gaffe -- that are as hard to predict or foresee as the sequence of events that begins when a butterfly flaps its wings.
