It's presumptuous to tell people to do something that might cost them their career, but:
I remember sitting in the gallery at a trial of some peace activists charged with trespassing at Rocky Flats, when it was a high-security nuclear weapons plant, and a retired general tried to testify on the activists' behalf that the USA had more than enough nuclear weapons, and therefore, Rocky Flats was superfluous and an environmental threat. The judge ruled the retired general's argument was irrelevant to the charge of trespassing and would not be admissible.
But, what I thought was "Gee, maybe people might have wanted to hear your message BEFORE you were a RETIRED general!"
I feel the same way about Corker and Flake. It's great that they are speaking out about Trump, but then they don't have anything on the line.
Trump has the emotional maturity of a 10-year-old. Instead of making excuses, it would be nice if Republicans leaders in a position of power would stand up to him and tell him so.