Johnny Mac may have staged a million-dollar raid on Rudy Giuliani’s home turf yesterday, but he shouldn’t get cocky just yet.  At RCP’s Horse Race blog, Jay Cost brings it (as usual):

McCain is staunchly opposed by a vocal group of conservatives who view him as an unreliable maverick. You can hear their most prominent advocate on the radio every weekday from noon to three eastern. You can see them in the exit polls, which show that McCain has not yet won a (statistically significant) plurality of Republican voters, nor those who consider themselves “very conservative.” In years past, opposition to the Republican frontrunner tends to fade away after South Carolina, with the supporters of the loser accepting that their guy can’t prevail and reconciling themselves with the victor. But that does not seem to be happening this year. There is a faction of the party that seems unwilling to accept McCain. It might be able to stop him.

It should be clear from the nomination rules that somebody could find enough delegates to oppose McCain on the convention floor – even if he did not offer a serious challenge early in the process. From the unpledged delegates, to the delegates allocated by conventions, proportional allocation, and the congressional district delegates – there are a lot of ways to win convention support even as somebody else “wins” states. Eventually, an opposition candidate would have to break through with outright victories. He cannot win the Republican nomination underground – but the way delegates are allocated could keep the race close until he breaks through. Importantly, about 65% of South Carolina voters preferred somebody other than John McCain. This tracks with his standing in the national polls. So, the anti-McCain faction might have an audience – if it can find a candidate to rally behind. Also of importance: 95% of all delegates have yet to be allocated. And even after Super Tuesday, 45% will remain to be allocated. The faction has time to make its case…

Cost explains why that will not be easy, and how the media might miss it happening, so McCain detractors and supporters will want to read the whole thing.