John McCain needed a deus ex machina. The deus—or rather, in this case, the dea—he found, sprung fully formed from the brow of Rush Limbaugh, is the governor of Alaska, Sarah Palin. The machina is “the base,” the Christianist conservatives who have come to dominate the Republican Party.
A cursory internet search (I'm not sure how any internet search can fail to be cursory but that's a topic for another day) suggests the word Christianist has been around for a few years, and seems to be constructed on analogy with Islamist, another neologism. If that's right, it means something like "theocratic types who turn Christianity into a dangerous fundamentalist ideology," and is designed to let presumably non-dangerous devotés of the religion distinguish themselves from those they think are perverting their presumably undangerous faith. The term may have been coined to designate Dominionists, but I don't think that's what Hendrik Hertzberg (author of the New Yorker column) has in mind...
