When Donald Trump ran for president, many Republican senators were reluctant to endorse him, with some even calling on him to end his candidacy. Now that Trump is in office, that reluctance isn’t visible in the way senators are voting: Republicans are, by and large, supporting the president.
Generally speaking, the worse Trump did in a Democratic senator’s state, the more likely that senator is to vote against Trump’s nominees and legislation that he supports. Republicans’ votes, on the other hand, don’t track at all with how their state voted in the presidential election. Instead, Republicans are mostly voting in line with the administration.
FiveThirtyEight’s Trump Score tracks how often each senator votes with the president. Trump’s position isn’t clear on every vote the Senate takes, so this analysis comprises 32 Senate votes: 19 were on Cabinet-level confirmations, and 13 were on the passage of bills and joint resolutions for which we know Trump’s stance.1
On those votes, the average Republican has voted with Trump’s position more than 99 percent of the time.2 The average Democrat has voted with Trump’s position about 27 percent of the time.
There’s a fairly straightforward explanation for the voting pattern so far: The Republicans have a slim majority in the Senate, holding 52 seats to the Democrats’ 48.3 Majority Leader Mitch McConnell is unlikely to allow votes on legislation or nominations that he knows won’t be successful, so things that come to the floor are all but guaranteed to get at least 50 votes — which means Republicans will end up voting together consistently. There’s less necessity for Democrats, as the out-of-power party, to vote together 100 percent (or close to 100 percent) of the time. Republicans can pass legislation and confirm nominees without any Democratic votes,4 as long as almost all the Republicans vote together. Republican defections from the party position, in other words, can kill a bill; Democratic defections from the party position can change only the margin by which5 a bill passes or a nominee is confirmed.
It’s also likely that some of the legislation being passed would have been passed by a Republican Senate even with someone else as president. Eleven of the votes included here were on rolling back regulations finalized toward the end of the Obama administration, for example. But Republican senators are also showing little resistance to voting for Trump’s Cabinet nominees.
We can compare how the Senate is voting in Trump’s first year (so far) with how it voted in the first year of previous administrations, with some caveats. The best historical data on the topic is compiled by George C. Edwards III, a political science professor at Texas A&M University. He looks at legislation that presidents took a position on and how legislators voted, giving them a score showing how often they voted with the president. The most comparable score in Edwards’s data is limited to contested votes — those on which the winning side got less than 80 percent of the vote.6
Limiting our data to contested votes leaves Republicans’ average agreement about the same. But the Democrats’ average changes drastically: While the average Democrat has voted with Trump’s position about 27 percent of the time on the 32 votes for which we know his position, on contested votes — of which there have been 23 — the average Democrat has voted with Trump’s position only about 9 percent of the time.
We can also see that in the first year of the past few administrations, while senators from the president’s party vote heavily in support of him — and senators from the opposing party heavily against — there are typically more defections than there have been so far this year.