It seems like he abandons principle the minute that he's out of political danger.
Warner was defeated in the first GOP Senate race in which he ran. That was 1978. I think that it was a primary, but it might have been a caucas selection process.
Unfortunately, the good conservative, who beat Warner and won the GOP nomination, died in a plane crash several months later. The party then turned to Warner as a replacement.
I gave money to Warner in 1984 when he ran for re-election, but never after he voted against Bork in 1986 or 1987, showing what a true RINO he was.
In 1994, Warner refused to back Oliver North, who won the GOP Senate nomination. But it was much worse. Warner recruited and actively backed another RINO, who ran as a independent against Ollie North and Dem candidate Upchuck Robbed. Warner betrayed the whole party and is unworthly of an ounce of loyalty, but I've reluctantly voted for him when the Dem had a chance of winning. Mostly, I voted for a third party candidate running against him.
I wouldn't say that he abandons principle. I would say that he is a blue-blood, to-the-manor-born, country club Republican. Many, but not all, of Warner's principles are in common with the WashPost editorial writers.
Warner has been embracing the democratic party for several years now.