This article at Harper’s argues that the rejection of the McCain/Palin ticket by mainstream Protestants that Steve Waldman described is a matter of theological as much as political differences (via Andrew Sullivan):

For the mainstream Protestant, Palin is engaging in what Reinhold Niebuhr calls “the idolatry of America.” As Niebuhr would have it, an American Christian may be patriotic and love his country, but he must also remember that his true home rests outside of these bounds fixed by geography and time and in an eternal community with Jesus Christ. The Christian’s commitment to his faith must come first, and it must transcend a commitment to the nation-state. This means that patriotism is, in the mainstream Protestant view, a fairly complicated matter. In particular, again in the Niebuhr tradition, a Christian must guard against the risk that vanity, haughtiness and hatred towards the balance of mankind enter into his heart under the guise of patriotism; he must retain a skeptical and critical attitude which recognizes the imperfection of human works. The perspective of Religious Right figures like Palin that elevates America—as their political blinders conceive her—to some sort of sacred object is therefore little short of an act of idolatry. Jesus Christ, as Charles Marsh reminds us, “comes to us from a country far from our own” and requires that believers lay their “values, traditions, and habits at the foot of the cross.” Or, as John Calvin says, “the heart is a factory of idols,” and a primitive noncritical form of patriotism can be a particularly troubling and entrenched idol.

I would love to attribute this level of theological sophistication in thinking about politics to my fellow mainliners, but color me skeptical. My guess is that mainline Protestants prefer Obama for much the same reasons as other people: the economy’s in the tank; we’ve just had 8 years of catastrophic Republican failures; and Obama has convinced them that he’s likely to be a steady hand on the ship of state.