They always fall in line.

Former Massachusetts Gov. Mitt Romney (R) will sign an anti-tax pledge supported by Americans for Tax Reform (ATR), the conservative group said Thursday.

Romney will sign the “Taxpayer Protection Pledge,” drafted by conservative activist Grover Norquist, which has become somewhat of a litmus test for Republican candidates at all levels.

This, by the way, is the same Norquist pledge that demands that Republicans reject not only tax increases, but also measures to eliminate tax credits, in the hopes of denying the government even a penny of additional revenue forevermore.

This wouldn’t be especially interesting — Romney panders to right-wing cranks? You don’t say — except the Republican frontrunner used to be so much more sensible about these issues. As a candidate in Massachusetts, Romney not only refused to sign a “No New Taxes” pledge, his campaign mocked such pledges a “government by gimmickry.” Now, apparently, Romney believes the opposite.

That previous iteration of Romney’s former persona might have actually made a credible presidential candidate.

Instead, it looks like the folks behind Multiple Choice Mitt have a new entry for their growing list.

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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.