The conventional wisdom says Mitt Romney’s biggest vulnerability as a presidential candidate is cowardly flip-flops, shamelessly taking both sides of every issue depending on which way the wind is blowing at the time. And to be sure, this speaks poorly of Romney’s trustworthiness and integrity.

But it’s not his only vulnerability. Priorities USA Action, a Super PAC that supports President Obama, released this absolutely brutal video this morning, going after the former Massachusetts governor on the economy. The flip-flops weren’t mentioned at all, because they didn’t have to be.

YouTube video

The 97-second video — too long for a broadcast ad — covers quite a bit ground, intending to show the viewer what America could expect from Romney presidency. We learn that the Republican frontrunner supports the Tea Party; ran an equity firm that laid off thousands of American workers; believes corporations are people; favors Wall Street; supports foreclosures; wanted to let Detroit go bankrupt; had an abysmal jobs record in Massachusetts; wants far-right justices on the U.S. Supreme Court; backs privatization of Social Security; and generally toes the party line on everything from Medicare to Planned Parenthood, climate change to student aid.

“There are a lot of reasons not to elect me,” Romney says in the clip.

There are a few angles to keep in mind here. The first is that the Democratic establishment is now effectively operating under the assumption that Romney will be the GOP nominee, and are going on the offensive now as if the general election is underway.

Second, this devastating message is a reminder that, as ridiculous as Romney’s flip-flopping has been, Dems can hammer the Republican on bread-and-butter economic issues that matter most to the American mainstream.

And third, while the right may not want to hear this, Priorities USA Action’s pitch is the kind of message that resonates with voters, precisely because it speaks to the broad economic concerns. It hits Romney where he lives — the former governor wants voters to see him as having credibility on the economy, and videos like these take that credibility away.

If this is the basis of the 2012 message, the president’s allies have a compelling and persuasive argument to make.

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Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.