David Plouffe, a senior adviser to the White House, appeared on “Meet the Press” yesterday and took a few pointed rhetorical shots at Mitt Romney. The result was a pretty big hint as to the kind of message voters are likely to hear in 2012 if the former Massachusetts governor wins the GOP nomination.

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For those who can’t watch clips online, Plouffe said this about Romney:

“[H]e has no core. And, you know, every day almost it seems to be we find another issue. You know, he was supportive of doing things like a cap and trade agreement, now he doesn’t think that, you know, climate change is real. He was to the left of Ted Kennedy on gay rights issues, now he wants to amend the Constitution to prevent gay marriage. He was an extremely pro-choice governor, now he believes that life begins at conception and would ban Roe v. Wade. So you, you look at — issue after issue after issue, he’s moved all over the place.

“And I can tell you one thing, working a few steps down from the president, what you need in that office is conviction, you need to have a true compass, and you’ve got to be willing to make tough calls. And you get the sense with Mitt Romney that, you know, if he thought it was good to say the sky was green and the grass was blue to win an election, he’d say it.”

I mention this in large part because Plouffe seems to understand that labeling a rival a “flip-flopper” just isn’t enough. It’s a start, but it’s not sufficient — much of the country is probably already inclined to believe that politicians are a bunch of hypocrites who are willing to say anything to get elected. For that matter, every candidate in every race has probably changed his or her mind on an issue or two.

The key for Democrats in 2012, however, is helping the country understand that Romney is a very different kind of animal. There are literally zero major issues on which the guy has taken principled, consistent stands. America hasn’t seen a candidate like him — a man totally free of convictions, practically allergic to core beliefs — in modern political history. The goal for Dems isn’t to label Romney a flip-flopper; it’s to label him a craven fraud with the stability of a candle flame.

Rank-and-file voters may not be able to keep up on the subtleties of Romney’s flip-flops on climate change and cap-and-trade plans, but the public cares about trustworthiness.

If voters ask themselves, “I like some of what Romney said, but will he say the opposite tomorrow?” then the Obama campaign has done its job.

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.