Funny you should mention that Jonah–I was just about to blog on it.
I agree that it is a “bad idea” to deny communion to Kmiec; indeed, it is wrong to deny it to him on the basis of his support for a politician who supports legal (and subsidized) abortion. I do not think the relevant distinction here is between politicians and non-politicians. The key question is whether a person, whatever his station in life, is willing justice for (among others) the unborn. If Kmiec had written column after column denying that unborn children have a right to life, then his status as a non-politician would not matter: Assuming his priest had alerted him to the problem, he would be obstinately persisting in grave sin (which is a canon-law standard for denying communion). But Kmiec has not done this. He has endorsed Obama even though he disagrees with him about abortion.
Based on Kmiec’s statements to date, he has weighed the injustice of abortion-on-demand against (what he regards as) the injustice of the Iraq war, and the likelihood that a McCain victory would reduce the former injustice against the likelihood that an Obama victory would reduce the latter injustice. I think Kmiec’s prudential judgment has gone seriously awry. (For one thing, even if you believe, as I do not, that Iraq is an unjust war, it is not generating a toll of 1.3 million unjust deaths each year.) But his actions, including his statements, are consistent with willing justice to the unborn, so there are no grounds for refusing communion to him.