It’s funny: In so many cases in last night’s Republican debate in Arizona, Rick Santorum gave more direct and less politically-driven answers than Mitt Romney offered. Yet Santorum’s replies were complicated and kept putting him on the defensive.

The discussion among the GOP candidates on earmarks was fascinating. After months and months in which all Republicans regularly bashed earmarks, each of the candidates — including libertarian Ron Paul — defended particular earmarks that they had sought for particular purposes. Never has an exchange so underscored how sweeping, popular rhetoric is usually misleading about what candidates actually think, and do.

Santorum gave a lengthy answer in which he explained why he had sought earmarks for Pennsylvania, and why, when earmarks began to be abused, he called for their abolition. He also made an entirely valid point: Romney has attacked him for pursuing earmarks even as Romney himself sought federal help, through earmarks, for the Salt Lake City Olympics and projects in Massachusetts.

Romney didn’t bother to the earmarks he had sought and just repeated his rhetorical salvos against the earmark process. The audience seemed to like Romney’s answer better.

Santorum’s problem is that what he said could be too easily parodied as a claim that he had been for earmarks before he was against them. That would unfair, of course, but sometimes complexity is simultaneously (1.) more accurate and candid, and (2.) not terribly effective politically.

This went to the most striking aspect of the evening: how often Santorum was put on the defensive — and seemed defensive. He began an answer explaining why he had been wrong to vote for the No Child Left Behind Act with the words: “I have to admit,” not a great way to open an argument. And rather than focus on the good reasons for voting for the law (and there are quite a few), he wrote off his vote as going along with his colleagues. “Sometimes you take one for the team,” he said. It didn’t sound like leadership or courage - the one word Santorum used earlier in the debate to describe himself.

Because of this, Romney won this debate if winning is measured by who most moved swing voters. Yet Romney was not a particularly attractive figure in the process. There was an unpleasant, slightly snide sniff when he turned to Santorum and said, “I’ve heard that line before.” When moderator John King asked what the biggest misconception was about each candidate, Romney didn’t even bother to answer the question, instead going into boilerplate campaign speechifying. When King called him gently on not answering, Romney replied; “You can ask the questions you want and I’ll give the answers I want.” I’m not sure how well that went over with viewers.

But it probably didn’t matter because Santorum missed his chance to take the fight to Romney, while Romney (with help from Ron Paul) kept Santorum in explaining-and-justifying mode.

Newt Gingrich was relaxed and effective, smoothly getting in the criticism of Romney on earmarks that Santorum was trying to make: Gingrich poked fun at “claiming what you got was great and what he got was wrong.” Gingrich also captured the underlying message of earmarks discussion when he said: “This is one of those easy demagogic fights that gets you in a lot of trouble.” But Gingrich did not seize control of the stage as he had in his best performances in South Carolina.

Ron Paul was Ron Paul, the more-or-less consistent libertarian (except on earmarks). Once again, he seemed to be a Romney surrogate, concentrating his fire on Santorum.

And one thing was abundantly clear: The Republican candidates, particularly Mitt Romney and Newt Gingrich, thought it more important to punish unionized workers than to save the Detroit-based auto industry.

Both sought to defend their opposition to the auto bailout by arguing that the United Auto Workers union was central to the industry’s problems and that bankruptcy was the most desirable outcome because it would have undermined the union. “The UAW would have lost all their advantages,” Gingrich said.

Not a word was said about the sweeping concessions the unions made to save General Motors and Chrysler. And neither faced up to the economic chaos that letting the auto companies go down would have caused throughout the Midwest. No wonder President Obama is ahead by 20 points in Michigan.