Apparently within striking distance in New Hampshire, and being touted in some circles as having an indirect route to the GOP nomination, John McCain has quickly become the center of Mitt Romney's attention. The two had an interesting exchange yesterday, with the former governor accusing the senator, fairly, of flip-flopping on taxes and immigration. McCain responded:

"I know something about tailspins, and it's pretty clear Mitt Romney is in one," said the former front-runner. "It's disappointing that he would launch desperate, flailing and false attacks in an attempt to maintain relevance."

The "tailspin" reference was, apparently, a reference to McCain's Vietnam service. It seems to be part of a pattern.

When McCain laments earmark spending, he emphasizes his Vietnam service. When he talks about military challenges in the 21st century, he emphasizes his Vietnam service. When he delivers a Christmas message, he emphasizes his Vietnam service.

It's a subtle theme, isn't it?

To be sure, by any reasonable measure, McCain's experience in the military during the war in Vietnam was heroic and demands respect. If he wants to use this part of his biography in the presidential campaign, it makes perfect sense -- like John Kerry, that's what war heroes do.

But let's not forget that, during the last presidential campaign, when Kerry reminded voters of his own heroic service, McCain criticized him for it.