If there are lingering doubts about the validity of the “no core” criticisms against Mitt Romney, one need look no further than what he communicated to Massachusetts voters before becoming a presidential candidate.

Peter Wallsten and Juliet Eilperin highlight this anecdote, for example, from a meeting Romney had nine years ago with abortion-rights advocates.

[A]s the meeting drew to a close, [Romney] offered an intriguing suggestion — that he would rise to national prominence in the Republican Party as a victor in a liberal state and could use his influence to soften the GOP’s hard-line opposition to abortion.

He would be a “good voice in the party” for their cause, and his moderation on the issue would be “widely written about,” he said, according to detailed notes taken by an officer of the group, NARAL Pro-Choice Massachusetts.

“You need someone like me in Washington,” several participants recalled Romney saying that day in September 2002, an apparent reference to his future ambitions.

Romney made similar assurances to activists for gay rights and the environment, according to people familiar with the discussions, both as a candidate for governor and then in the early days of his term.

It’s important to appreciate what, exactly, Romney was saying at the time. His pitch to these center-left advocates was that he, a moderate Republican, could slowly work his way into the national GOP spotlight, and in time become a key player, able to shape the Republican Party’s agenda. And if they supported him, they would help empower Romney to change his party, moving it to the left in the coming years.

As Jon Chait put it, Romney “was promising behind closed doors to act as essentially a sleeper agent within the Republican Party, adopting liberal stances, rising to national prominence, and thereby legitimizing them and transforming the Party from within.”

There are a few key takeaways from a story like this. The first is that Mitt Romney has such deep character flaws, I don’t think Americans have seen a politician this craven in a very long time.

Second, if Romney’s rivals for the GOP nomination don’t immediately pounce on this, they’re guilty of political malpractice on a near-criminal level.

And third, I suspect there will be some Romney-loving Republicans who read the Post article and think, “Boy, Romney sure did pull a fast one on those liberals activists! It was smart of him to use them to get ahead.”

But therein lies the rub: how do they know — how does anyone know — which side Romney is lying to? Was he lying to his Massachusetts constituents about helping move the Republican Party to the left, or is he lying to the GOP base now about helping moving the country to the right?

The fact that no one can say for sure seems pretty important.

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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.