To see why, think back to the 2004 presidential debates. Back then, the pundits declared John Kerry the winner of his debates with George W. Bush. Kerry was more articulate than Bush and seemed in greater command of the issues. But unlike Bush, Kerry made a devastating gaffe when he declared that any presidential decision to go to war must first pass a “global test” of legitimacy. Bush seized upon the remark, and it became a staple of his campaign speeches -- and fodder for this devastating campaign ad:

After being pummeled for the remark, an exasperated Kerry was left sputtering: “It’s almost sad; it’s certainly pathetic, because all they can do is grab a little phrase and try to play a game and scare Americans.”

Mitt Romney was the John Kerry of tonight’s debate. He was far more articulate than Perry (who flubbed what should have been an easy attack on Romney’s flip flops). But it was Romney who made the gaffe that will almost certainly appear in campaign ads that are probably being written as you read this, when he declared: “There are a lot of reasons not to elect me.”

You can see the ad already:

Announcer: Barack Obama has called Mitt Romney’s healthcare law in Massachusetts the model for Obamacare.

Romney: “There are a lot of reasons not to elect me.”

Announcer: Romney’s own Chief Economic Advisor said Romneycare “Imposed a Very Large Burden on Small Businesses and Their Employees”

Romney: “There are a lot of reasons not to elect me.”

Announcer: Romneycare Killed 18,000 Jobs and cost taxpayers $8 billion

Romney: “There are a lot of reasons not to elect me.”

Announcer: Little wonder that after four years under Mitt Romney, Massachusetts was 47th in the country in job creation -- third from last in the entire country.

Romney: “There are a lot of reasons not to elect me.”

And so on and so forth… insert any attack you like.

If Perry does not run such an ad in the primaries, you can bet Barack Obama will in the general. So yes, by Cambridge Union standards, Romney may have come out the winner. But like John Kerry before him, the more articulate debater produced the gaffe that will be used against him in ads and speeches for months to come.

Marc Thiessen writes a weekly column for The Post on foreign and domestic policy and contributes to the PostPartisan blog. He is a fellow at the American Enterprise Institute, and the former chief speechwriter for President George W. Bush.