John Schwenkler points us to this summary of an appearance by Rick Santorum at the Oxford Center for Religion and Public Life:

After he’d accused Obama and other Democrats of religoius fraudulance for a few minutes, journalist Terry Mattingly of asked whether it’s possible that rather than being fake, perhaps,Obama was sincerely reflecting a form of liberal Christianity in the tradition of Reinhold Neibuhr. Santorum surprised me by answering that yes, “I could buy that.”

However, he questioned whether liberal christianity [sic] was really, well, Christian. “You’re a liberal something, but your not a Christian.” He continued, “When you take a salvation story and turn it into a liberation story you’ve abandoned Christiandom [sic] and I don’t think you have a right to claim it.”

The troubling thing I find in the summary is not that a Republican imputes bad (or rather non-existent) faith to professing Christians in the other party, since it is also pretty much standard fare for liberals to get on their own soapboxes and assure everyone that real Christians could never support a given GOP policy, or they may insist that it is hypocritical to confess Christ and endorse, say, tax cuts.  (Sometimes, when it comes to things as heinous as legal abortion, torture or aggressive war, there is certainly a valid argument that Christians shouldn’t support such things, but that would apply to Christians on both left and right.)  It’s not a particularly attractive habit, but it is one that we come to expect from partisans.  What I find troubling is that Santorum feels free to see-saw between the correct understanding that he cannot know–and should not judge–whether Obama’s faith is sincere and the partisan talking point that he joined his church only for political advantage.  God alone knows all the reasons why Obama joined his church, and if that’s true you cannot conclude categorically that Obama joined his church simply for political gain.  (Was there a political dimension to his membership?  Of course there was, and it would be a bit surprising if that weren’t somewhat true for politically engaged conservative Christians as well.)

In fact, Santorum’s critique of liberal Christianity as theologically deficient or misguided is where he is on the strongest ground, because doctrine is something that can and should be assessed critically.  It is quite reasonable to conclude that Obama, among others, is a sincere liberal Protestant who is therefore going theologically awry because he is a sincere liberal Protestant, but you cannot simultaneously find fault with his doctrine while also saying that he doesn’t really believe it and then expect to be taken seriously.  It is one thing to say that a given church or doctrine lacks the fullness of the truth and is therefore necessarily spiritually lacking, but it is something else all together to claim that those who believe in that doctrine are engaged in a massive fraud by merely pretending to believe.  The first is a reasonable, defensible position, while the second is pretty much baseless character assassination.