Privately, one of the GOP's biggest givers told CBS News, "If George Bush loses South Carolina on Saturday, I would expect him to lose Michigan on Tuesday and then it would be all over for Bush."
Governor Bush claims he's in good shape with Republicans, but that may not be enough, reports CBS News Correspondent Phil Jones.
In a news conference Bush conceded, "I do hear some concern among Republicans that it's going to be the Democrats that determine the election."
And there is reason for Bush's concern. In 1996, Democrats and Independents made up almost one-third of the total Republican primary vote.
Thursday, John McCain continued to court non-Republicans. He saw no reason to be apologetic: "I've been sort of criticized by the fact that we are attracting Independents and Democrats. My friends, I'm proud. I'm proud, I'm proud that anyone would flock to our banner."
Democrats who are showing up at McCain rallies deny charges from the Bush camp that they are up to mischief by voting for the Republican who'll be the weakest in November.
Elrae Poucher, a Democrat who now supports McCain, insisted, "I don't think that most of the cross-over votes are mischief makers. I think the man has inspired us - it has united us."
If McCain has a chance of winning, he must have the support of Independents and Democrats. His aides said Thursday that they have several thousand volunteers, buses and an e-mail network aimed at getting these voters out on Saturday.