Rick Santorum appeared on “Face the Nation” on Sunday. In this appearance you see vividly the problems with his candidacy: a defensive prickliness, his controversial stances on social issues that crowd out other topics (there wasn’t time to discuss the economy after giving him time to untangle himself from a series of comments), and the stridency of his beliefs, which will strike many voters as extreme if not downright bizarre:

His ability to take mainstream conservative views (opposition to extreme environmentalism) and voice them in radical and intemperate rhetoric is essentially a model of “how to alienate skeptical voters.” If you accuse the president of having a “phony theology” you better be prepared to be taken for a religious zealot. And if he wants to play think tank scholar (in this case, talking about the secular substitution of various value systems in place of religion) he should get off the trail and speak much more precisely. (He often sounds like a man who’s read some smart conservative scholars but hasn’t the depth of understanding nor the finesse to express the ideas he’s read without sounding nutty.)

His position on prenatal testing amounts to: “I don’t trust parents to makes a decision, so we shouldn’t give them information.” (He should chat with Sarah Palin, who learned her baby would have Downs Syndrome and was able to prepare herself and her family for the challenges ahead.)

His statement regarding the president’s view of disabled people is, once again, the sort of explosive language that will inflame, anger, and put off voters. You can say Obama has an extreme position on abortion without suggesting he hates disabled people. The latter is not going to endear you to undecided voters.

On the subject of schools, he yet again has a valid point: The public schools aren’t working well. But his aversion to having even states decide curriculum again takes a popular position and puts voters on edge. While virtually every parent wants schools to be more responsive, do we really think that, outside of home schooling, each child is going to have his very own curriculum? (By the way, since he keeps his kids out of schools he may be ignorant about the trend in recent years toward “differentiation.”) Moreover he should have thought about this when he voted for No Child Left Behind, which greatly increased the role of the federal government in schools. Now, we certainly want parents involved in their children’s education, but do we want them entirely controlling the curriculum? (What if parents in Hyde Park want to teach their kids American history according to Noam Chomsky?)

Running through Santorum’s statements is a common failing. Santorum says controversial things couched in the harshest terms possible. When he’s misunderstood (or even understood correctly but greeted with shock) he complains that the media are twisting his words or fixating on a few small issues. A presidential candidate must communicate clearly, forge a coalition and develop a reputation for sound judgment with the voters. Santorum seems not even to understand that this is what is required to win a national contest.

If he doesn’t understand the task — let alone show the ability to get it done — how in the world would he get through a general election campaign?