You know, I remember the McGovern campaign. I was a big supporter of McGovern's, and I hated Nixon, as did all of my friends. And the scenario then was completely different from what you are seeing now. We were never excited about Eagleton in the first place. We just wanted McGovern to win. Eagleton didn't infuse new energy into the McGovern campaign or jazz up am important subset of voters. He was just some boring Senator that got slotted in. And then he brought nothing but trouble and distraction as the news came out that he'd been hospitalized for depression 3 times and had receive electroshock treatments. It wasn't just that there were a couple of old political controversies or a family member was less than perfect. We were getting significant new information about his brain, the brain that we might need to rely on to make presidential decisions. It was simply not acceptable, especially since he'd also withheld this information from McGovern, which showed some really poor character.
It should also be remembered that McGovern didn't come out looking very good, either. First, he said he was behind Eagleton "1000%"--then, two weeks later, he tossed him under the bus. Didn't make McG look very steady in a crisis. Even McGovern now admits that was a colossal mistake on his part.

McCain does not strike me as the sort of person who would bail on Sarah just because a bunch of Kos Kiddies have gone all attack-dog on her
The Palin candidacy has virtually nothing in common with the Eagleton scenario, and the people who are saying it does are displaying their desperation. Obviously -- I'm not the first to say this -- if you want McCain to lose and you think she's so terrible, you should be happy to see Palin as the VP nominee. It will help defeat McCain.