Candidates who abandon their national ticket can often keep getting re-elected in their state if the national ticket is out of sync with the state's party, but it still kills their chances if they want to run for President. This is exactly what happened to Rockefeller, he turned to the right after 1970, but it was never enough for the GOP's conservatives, who never forgave his apostasy. Democrats who were silent on McGovern were some of the first casualties of the 1974 move by the Democratic caucus to end the seniority system. I cannot think of a single Presidential or Vice Presidential nominee of either party who bucked their party's Presidential nominee by refusing to support them, and made it onto the ticket after that. Indeed, until this year, the only ticket members who I can remember not endorsing the nominee AFTER being on the ticket were Joe Lieberman (who actually campaigned for McCain and was almost HIS VP candidate) and MAYBE John Sparkman in 1972.
And yet, despite this history, many Republican politicians (not just Kasich) last year publicly said that they wouldn't vote for Trump:
https://uselectionatlas.org/FORUM/index.php?topic=230807.0All of these folks either 1) have no interest in running on a national ticket in the future, and are content to hold onto their current office forever, 2) don't think the history you cite is relevant to their situation, for whatever reason, or 3) are principled enough that they're willing to risk their own ambitions because they think Trump is sufficiently terrible that they had to speak out against him.
I mean, that's the full range of logical possibilities, right? What's the fourth option? That some of these folks actually thought Trump wouldn't be the nominee anymore by election day, because he'd quit over the Billy Bush tape or something?
