A couple of things here:

1) Bob Corker is retiring, so he's no profile-in-courage.

2) Corker votes with Trump about 85% of the time, at the lower end of the cult, but mostly pushing the same destructive agenda as the rest of them

Source: NBC

Sen. Bob Corker, the Republican chairman of the Foreign Relations Committee, on Wednesday chided his GOP colleagues for being "cultish" and "fearful" under President Donald Trump, and said some are concerned about their prospects in the midterm elections.

The Tennessee lawmaker said there are a number of reticent Republicans who are afraid to push back at Trump because they do not want to agitate the president.

“We are in a strange place. It’s almost, it’s becoming a cultish thing, isn’t it?" said Corker, who also sits on the Senate Budget Committee. "It’s not a good place for any party to end up with a cult-like situation as it relates to a president that happens to be of, purportedly, of the same party.”

He added, "We have a lot of people who are willing to do the things that they feel are right for our country. We have some who are fearful of upsetting the president. But it’s not a good place for us to be."