Let's say that the fears of most voters come true and the Republican Presidential nominee, Senator John McCain of Arizona suffers some severe health issue (possibly a heart attack) that incapacitates him. Assuming that this occurs sometime after the Republican National Convention, would the Republican National Committee nominate the second place winner, Former Governor of Massachusetts Mitt Romney, or McCain's Vice Presidential nominee, Governor of Alaska Sarah Palin? Probably not, because she did not win any of the primary contests. If the Committee did select her, who do you think her own Vice Presidential nominee would be? How well do you think she'd do against Obama-Biden in November? I'd imagine someone moderate after showing the world her views.
A Palin candidacy would be the nail in the Republican coffin of 2008.

Even though by then she had a somewhat starched reputation, to put it kindly, and she would seem repugnant to an American public that was tired of Republicans.

Obama's victory would be even more secure than in OTL.
Palin would suffer even more humiliate defeat than McCain.

And this might rip Republicans.