Liberals WILL maintain party loyalty as you say. They DO NOT necessarily back the most liberal candidate -- if they did, Dennis Kucinich would have been the nominee in 2004. Bill Clinton was certainly not the most liberal nominee in 1992; Carter was not the most liberal nominee in 1976.
Parties generally nominate the candidate from within their ranks that has the best chance to win. The idea that some ideology is the overriding criterion for the primaries is ludicrous. Think GHWB was the most conservative in 1988? Dole in 1996? Bush in 2000? Ford in 1976? Nixon in 1968?
Also, many liberals in 2000 did NOT vote for the guy with the "D" next to his name. They voted for Nader. Dumb, dumb move on their part -- but I'm glad they did such a foolish thing.
You make my point for me. Our last landslide victory was the most conservative candidate.
Ran on Reagan's coattails. Lost in 1992 when he drifted leftward.
Dole in 1996?
Lost.
Bush in 2000?
He was pro-life and not a gun-grabber and held the party together.Ford in 1976?
Lost.
Nixon in 1968?
Won only because of a rift in the Dem party.
Nice job of showing the dangers of leftward drift in the GOP.