Vote studies: 2025 sets new mark for partisanship on Capitol Hill

WASHINGTON — With President Donald Trump back in the White House and his party controlling the House and Senate, 2025 was the most partisan year for Congress in the history of our study in terms of floor votes, and it wasn’t even particularly close.

A whopping 85.3% of roll call votes were party unity votes — those with a majority of each party facing off on opposite sides. That’s more than 10 percentage points higher than the previous record of 74.6% in 2023.

The results point to the changing dynamics of the Senate, where the parties have each become more partisan aligned over the years, and where Senate Republicans voted together an average of 96% of the time on unity votes — only 1% less than the record they set in 2017.

The sweeping GOP-led reconciliation law that extended and expanded the 2017 tax cuts is perhaps the most striking example of party unity votes in 2025. The measure was a top priority for Trump and congressional Republicans and cleared Congress without a single Democratic vote. But it tells only part of the story.

Senate GOP success story

Senate Republicans had a blockbuster run last year, winning 577 of the 616 total party unity votes (93.7%).

That’s by far the most success they’ve had, both in the number of raw victory votes (1995’s 345 was their previous high, number-wise) and percentage (89.7% in 2017 — Trump’s first year in office — was their previous high mark).

The only win rate higher by a Senate majority was the Democrats’ 94.5% in 2024.

The GOP majorities in the House and Senate during the first year of Trump’s second term in the White House, though narrow, helped fuel the advancement of the president’s nominees and legislative agenda.

“The American people gave President Trump a mandate to deliver on his key priorities: securing the border, rebuilding our defense, and unleashing American energy,” Senate Majority Leader John Thune, R-S.D., tweeted in February 2025. “The time to act is now, and Senate Republicans are ready to roll.”

Of the 577 victories for Republicans, 338 came on nominations, while 86 were on votes related to enacting the sweeping reconciliation bill (and the two fiscal 2025 budget resolutions that preceded it).

The Senate also saw both parties set a record for unanimous party unity votes. Republicans completely united on 429 (70% of the 616 unity votes), and Democrats on 416 (68%). Those counts bested their previous records of 160 and 364 unanimous votes cast, respectively, with the other party standing in opposition.

The Senate cast an abnormally high number of recorded votes overall, thanks not only to the record number of roll call votes on Trump’s nominations, but also in large part to three official vote-a-ramas related to budget resolutions and the reconciliation bill.

The vote-a-rama on the GOP’s signature reconciliation measure, dubbed the “One Big Beautiful Bill,” yielded 43 roll call votes, tied for the second-most of any such vote marathon, according to an accounting by the Senate historian that goes back to 1980, with 40 of the 43 — 93% — being party unity votes.

Slim House majority sticks together and wins (usually)

In the House, Speaker Mike Johnson of Louisiana and Republican leaders had high-profile setbacks, including defeats on procedural votes to move bills to the floor. Disagreements within the caucus unrelated to legislation also spilled out onto the House floor.

And while a few unraveling plans to bring legislation to the floor prompted headlines about the speaker potentially losing control of his caucus, in many cases, the floor fracas resulted in delays not outright abandonment of leadership’s plans.

For example, in April, a small group of Republicans sought to bypass leadership in an effort to allow recent parents to vote by proxy. While the group, led by Florida Rep. Anna Paulina Luna, ultimately fell short of their goal, they did succeed in derailing a leadership move to quash their effort through language in a resolution primarily designed to set the stage for GOP-led voter ID legislation. The band sided with Democrats to defeat the floor debate resolution, delaying consideration of the voter ID bill in the process.

The House eventually came back around to the election measure, but only after canceling its work for the week.

GOP leaders also hit some speed bumps trying to wrangle a sometimes fractious conference with a narrow majority.

More than the usual amount of arm-twisting was sometimes required for the year’s significant legislation, including on votes setting up floor consideration of the fiscal 2026 defense authorization and legislation to roll back certain Consumer Financial Protection Bureau regulations.

That trend marks a change, longtime House Republicans said.

“I’ve been here long enough to remember that you could do anything you wanted, but you didn’t vote against a rule,” Rep. Rick Crawford, R-Ark., said in January. “And at that time, there were consequences for that type of action.”

“We have about 20 people that … created havoc, and they take down the rules of bills they like, just to prove another point,” Rep. Don Bacon, R-Neb., said of the trend of Republicans voting against rules. “It’s unfortunate. They’re independent actors, they’re not team players.”

Despite that, the House GOP leadership was able to keep their rank and file together an average of 95% of the time on party unity votes, and come out victorious on more than 90% of them. That rate of success was largely in line with how they did as part of the unified Republican government in the first half of Trump’s initial term.

The Republican record of success in the chamber is the 92.1% clip they set in 2018. But the party unity high-water mark of a unified government belongs to the Democrats. It dates back to the 2009 successes of then-Speaker Nancy Pelosi, D-Calif., when Democrats in Congress set the record at 94.2% during the first year of President Barack Obama’s administration.

Democrats also aligned

The average Democratic unity rate, meanwhile, was 93% in the House and 92% in the Senate.

All told, 34 House Democrats eligible to take part in all 254 of the chamber’s unity votes sided with the majority of their caucus on every one they cast.

Just three of the Senate Democratic Caucus members did likewise: Sens. Patty Murray of Washington, Tina Smith of Minnesota and Chris Van Hollen of Maryland.

Among Republicans, 14 senators who were eligible to weigh in on at least half of the chamber’s unity votes had perfect records of support, while 29 representatives did the same.

Methodology

The numbers are somewhat unavoidably inflated by the number of party unity votes on procedural questions: the metric counts both cloture and confirmation votes on the same nominations, and cloture votes have become almost perfunctory.

Ever since the Senate changed precedent to enable simple-majority cloture for nominations, confirmations have become more partisan.

Party unity votes occur, under the CQ Roll Call definition, when a majority of one party, counting independents who caucus with the Democrats, votes against the majority of the other party. Votes that are broadly bipartisan do not count here, though they may count in the presidential support tabulations.

Congressional Quarterly has been tabulating party unity scores for Congress since 1953.

Leaders in bucking their party

There’s predictable overlap between the presidential support scores unveiled last week and party unity scores.

Rep. Henry Cuellar, D-Texas, was the most likely House member to oppose his party, on either side, doing so 35.9% of the time. He was similarly the most likely in his party to back Trump.

Washington’s Marie Gluesenkamp Pérez (31.1%), North Carolina’s Don Davis and Maine’s Jared Golden (both siding with Republicans on roughly 30% of unity votes) are next on the list. They too were among the House Democrats most likely to back Trump.

In the Senate, Pennsylvania Democrat John Fetterman has effectively taken the mantle from former West Virginia Sen. Joe Manchin III as topping the list of Democrats most likely to vote against his own party, doing so almost 20% of the time.

New Hampshire Democrats Jeanne Shaheen and Maggie Hassan also bucked their party more than 15% of the time. Independent Sen. Angus King of Maine, who caucuses with the Democrats, was a much less reliable Democratic vote (breaking on 92 unity votes — 15% of those he cast) than Vermont’s Bernie Sanders, who voted against Democrats on just two such occasions.

Among Republicans, Rep. Brian Fitzpatrick of Pennsylvania led the way for breaking with his caucus (on 18.9% of unity votes), just as he did with the presidential support scores, where he went against Trump almost one-third of the time.

This isn’t the first year Fitzpatrick has topped the list of House Republicans in breaking from the pack; in 2024 he broke from fellow House Republicans 28.1% of the time to hold the top slot.

But among House Republicans, the switch from a Democratic administration to a Republican one shook up rest of last year’s top 10.

Rep. Thomas Massie, R-Ky., who wasn’t in the top 10 in 2024, came in second in 2025, opposing his party on 11.7% of the votes included in the study. Rep. Mike Lawler, R-N.Y., who was third in 2024, held the same position last year but broke with his party less: In 2024, he opposed his party 18.6% of the time, while in 2025, he broke 9% of the time.

In the Senate, meanwhile, the Republican defector leaderboard is as one might expect: Sens. Lisa Murkowski of Alaska, Susan Collins of Maine and Rand Paul of Kentucky led the way.

Murkowski went against the Republican position on 13.4% of her party unity votes, while Collins came in second with 12.7% and Paul rounded out the top three at 11.8%.