How to tell Mitt Romney is no 'wimp'? Take that, Harry Reid.

Suddenly, Mitt Romney is talking tough.

In a radio interview with Sean Hannity on Thursday, Mr. Romney was asked about Senate majority leader Harry Reid’s allegations that an unnamed Bain Capital investor had told him that Mr. Romney had not paid any taxes for 10 years.

Romney’s response: Senator Reid should “put up or shut up.”

Yes, the famously straight-laced GOP nominee – who, in what we’re sure is a massive coincidence, was recently labeled a “wimp” on the cover of Newsweek – is now using lines reminiscent of a Clint Eastwood movie.

At least he didn’t say “shove it” or “kiss my [posterior]” (that was just his press aide).

Still, it made us squirm a little.

Not because Romney’s choice of words violated any sort of political decorum. These days, politicians routinely use far saltier language than that, and often the public seems to like it. New Jersey Gov. Chris Christie’s blunt retorts – such as calling an opponent "an arrogant S.O.B." or telling coastal residents resisting a hurricane evacuation to “get the hell off the beach” – are widely seen as part of his appeal. Vice President Joe Biden famously dropped an f-bomb (albeit when he thought he couldn’t be heard) at the signing ceremony for the president’s health-care reform bill.

Romney’s not even the first politician to use “put up or shut up.” In late 2010, Sen. Mark Warner (D) of Virginia used the phrase on the Senate floor, talking about the need to address the debt crisis (though he added “excuse the language”). And former British Prime Minister John Major may be forever associated with the phrase, which he uttered at a press conference in 1995, daring opponents from his own party to try to topple him.

It’s just that it seemed, well, out of character for Romney.  

Tellingly, Romney didn’t deliver the line with anything even approaching genuine outrage. Listening to the tone of his voice, he could have been talking about his lawn furniture. Or the weather. Right before he said it, he emitted the same nervous chuckle that he makes whenever an interviewer brings up a topic he doesn’t like (a laugh that James Lipton, host of "Inside the Actor’s Studio," called “inert” and “mirthless.”)

It’s too bad, because this was a moment when Romney could have shown some real emotion. Reid has come under fire for making his accusation – which he first offered up in an interview with the Huffington Post – based on information from a sole source that he refused to name. In the same interview, Reid even acknowledged he was “not certain” it was true.

Even “Daily Show” host Jon Stewart – generally not a big Romney defender – called it a cheap shot: “You’re the Senate majority leader! You can’t just run to the Sideboob Gazette with ridiculous speculations about what may or may not be in Mitt Romney’s taxes!”

But instead of scripted rejoinders, what voters really need to hear from Romney is some sort of heartfelt response. It doesn't have to be snappy; it just has to be honest.

It’s telling that, at a point in the race when he most needs to let the public know who he really is, Romney seems to be doing the opposite. Instead of finding his voice, Romney keeps borrowing someone else’s.