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 percent 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 percent 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 percent of the time on unity votes — only 1 percent less than the record they set in 2017.
