On Tuesday night, seismologists at the Las Vegas Oceanographic Institute reported the first recorded movement of a hair on Mitt Romney’s head. These same scientists also detected signs of life in Rick Perry.

Such were the highlights of Tuesday’s seven-person Republican brawl at the Venetian. To be sure, there were other developments: Herman Cain stumbled, Newt Gingrich grinned, Rick Santorum landed a clean shot at Romneycare and Michele Bachmann made a spirited bid for a comeback.

But the main event was the scripted Perry attack on Romney, reprising the old charge of hiring illegal immigrants.

Perry’s accusation of rank hypocrisy had its effect. From the ensuing melee emerged a singularity: a ruffled Romney, face flushed, voice raised.

True, his unflappability is, to some, less reassurance than a sign of inauthenticity. But if you are going to show passion, petulance is not the way.

Worse, Romney turned to the referee — moderator Anderson Cooper — with a plaintive “Anderson?” seeking intervention. An uncharacteristically weak moment. What does he do when Vladimir Putin sticks a finger in his chest at a summit? Call for a journalist?

On substance, Romney remained as solid as ever, showing by far the most mastery of policy, with the possible exception of Gingrich — but without the lecturing tone and world-weary condescension.

Romney’s command was best seen in his takedown of Cain’s 9-9-9 plan. Cain refused to concede the burden to consumers of a national sales tax added on to state sales taxes. His national sales tax is a solution to a federal problem (a monstrous tax code), he insisted, and therefore irrelevant to any discussion of state sales taxes, which would exist regardless.

It took Romney one sentence to expose the sophistry. He simply pointed out that a real-world consumer with a basketful of apples and oranges would be paying the sum of the two sales taxes at checkout. Q.E.D.

Cain remained, as always, charming, engaging, confident and good-willed, the only person on stage other than Bachmann who didn’t have a sour or a nasty moment.

But his tax plan collapsed under fire in about 10 minutes, the coup de grace being delivered by Gingrich, who, when asked why the Cain plan is a hard sell, replied, “You just watched it.” It was the deadliest line of the night.

However, the principal drama was provided by Perry. His aggressive performance brought him back into the game, especially because he now has a few weeks before the next debate to deploy his major assets: a talent for retail politics and a ton of money. But the price of re-entry was high. His awakening wasn’t pretty. He showed he can draw blood, but it was a nasty schoolyard punch-up.

In primary races, personal attacks often have the effect of diminishing both candidates. This happened in 2004 in Iowa when Democratic front-runners Dick Gephardt and Howard Dean knocked each other silly, allowing John Kerry and John Edwards to sneak past.

Nonetheless, because of his considerable resources, Perry, by merely stirring himself, is back. But he hasn’t solved his problem. It’s not just that, as he readily admits, he’s not very good at debating, although that in itself is a huge liability.

It wasn’t before 1960. It is now. And based on Perry’s first five performances, Barack Obama would eat him alive.

But Perry’s often clueless responses betray an even deeper problem: He simply hasn’t thought through issues on a national scale. He is still Texas. And Texas simply isn’t enough.

That was most glaringly evident during the Dartmouth debate when, in response to questions about China and then about health care, Perry sought refuge by talking instead about his energy plan.

The Vegas fight mildly unsettled the GOP race. But its central dynamic remains.

It awaits the coalescence of anti-Romney sentiment around one challenger. Until and unless that happens, it’s Romney’s race to lose.

Charles Krauthammer is a columnist for The Washington Post and a regular panelist on PBS and Fox News. He can be contacted at: letters@charleskrauthammer.com