When Bush was trying to pass his No Child Left Behind bill, he called then-Congressman DeMint into the Oval Office and pleaded with him to avoid a blood bath" over an amendment he had added to the bill. DeMint still voted against NCLB, but dropped the amendment because of Bush's "gentle persuasion."
... But things were different when it came to passing Medicare. As DeMint recounts the story,
After publicly expressing my opposition to this bill, I was once again invited to meet with the president along with several other conscientious objectors. In that meeting the President made it easy for me; he threatened me by telling the group, "some of you have tough elections and we are watching how you vote." And he looked straight at me when he said it.
... You may have wondered how so many conservatives were co-opted into voting for bad legislation. I think this answers the question.
Fortunately for DeMint, he resisted the pressure, and was rewarded by being elected the the U.S. Senate, where he is one of a hand-full of reliably conservative senators...