Republicans in Congress have been very loyal to Trump. Will it last?

But Trump’s approval rating might have to take a nose dive before Republicans defect. While it’s unclear how voting patterns will shift in the new Congress, what is particularly striking is just how effective Trump has been in securing party loyalty in the first two years of his presidency. As you can see in the chart below, Senate Democrats didn’t coalesce as neatly around Obama during his first two years in office as Senate Republicans did around Trump.

George C. Edwards III, a political science professor at Texas A&M University, has collected historical legislative data from previous presidencies, comparing the president’s stance on a bill with how a senator voted on it. Specifically, Edwards captured how a senator voted on “contested” legislation — bills on which the winning side received less than 80 percent of the vote. (This metric isn’t exactly the same as our Trump score, so the chart above limits the votes its using to Edwards’ “contested” criteria.) On these votes, the average Republican voted with Trump 96 percent of the time, while the average Democrat voted 90 percent of the time with Obama’s position in his first two years. That may be because Trump’s White House and GOP leaders in Congress are more skilled legislative stewards or because of the sorts of bills that made it to the floor. It may simply be because times are more partisan now.