McCain’s natural constituency is the bookers on Hardball With Chris Matthews, or any other public-affairs show; he is “controversial,” while usually managing to say what the media wants to hear. In 2000, it became clear his grand goal was to blow up the current Republican coalition and craft something new, although it was left vague what exactly. He has never demonstrated great affection for social conservatives, whom he blasted in 2000. But he can work around these things. He recently endorsed teaching Intelligent Design in schools, although he probably has as much sympathy for this critique of evolution as the New York Times editorial board does.
McCain will be the strongest performing Republican against Hillary Clinton in early opinion polls; if anything, he is more aggressive on the war on terror than Bush is; he will have a strong theme of returning to a cleaner Republicanism after the ethical lapses of the current congressional majority. And all of this will be wrapped in his appealing thematic mix of patriotism, sacrifice and duty.
The problem for McCain is that he has such a richly layered history of apostasy, including on conservative gospel like the Bush tax cuts. Some of it is of recent vintage, for instance the enforcement-less immigration bill he is co-sponsoring with Ted Kennedy. A strong conservative candidate who unites the Right can take him down. But for that candidate, the less conservatives nod their heads at anything McCain has to say, the better.