I can tell you, at least in the case of Daschle, that his career could've been stopped dead in 1986. The reason why Jim Abdnor and Larry Pressler went down can be answered in 2 words: Bill Janklow. Janklow sabotaged both of the men because he didn't want to share the spotlight with any other Republican in major office in SD. It's no wonder that Daschle appeared as a character witness at his manslaughter trial. And for those that say Janklow was a Conservative and that it's impossible to be a RINO and a Conservative at the same time, I say it is possible. Janklow is living proof of that.
Sad story. My guess is that this kind of scum can be caught, and weeded out of politics, by alert higher-ups in the party early in their careers. Too bad it didn't happen to Janklow before his career got going.
You make a very good point there. Some politicians vote a good Republican line, but still cannot be counted on to be loyal to the party in a pinch. There are indeed different types of RINOs.