They call them "RINOs." Why? Here's a good example:
"Earlier this month, Sen. Chuck Hagel (R-NE) criticized Sen. John McCain’s (R-AZ) choice of Alaska Gov. Sarah Palin as his running mate, telling the Omaha World-Herald that “it’s a stretch to, in any way, to say that she’s got the experience to be president of the United States.” In a recent interview with The New Yorker, Hagel went even further, saying that he doesn’t believe Palin is “qualified to be President of the United States."
Senator Hagel claims, anyway, to be a Republican. He knows there's an election going on right now. He knows the man he's claimed in the past to respect, John McCain, needs all the help he can get. So why does he say something, publicly, that he knows can and will hurt the campaign?
Because he's a Republican in name only, that's why.
Why don't you just join the Democratic Party and get it over with, Sen. Hagel? We'll be fine without you.