New Jersey Gov. Chris Christie (R) has arguably been Mitt Romney’s most trusted and highest-profile campaign surrogate. Talk of Christie possibly serving as the Republican frontrunner’s running mate has been extremely common.

It was remarkable, then, to hear the governor on NBC’s “Today” this morning, pressing Romney to release his tax returns.

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For those who can’t watch clips online, here’s the exchange:

LAUER: You’re a full disclosure guy. You like it when politicians get out there and reveal their financial situations and their tax returns. Is mitt Romney missing the boat on this?

CHRISTIE: I don’t think he’s going to. I think he will release the taxes.

LAUER: Why wait?

CHRISTIE: Well, listen, I think the most relevant information is the most recent information. He’s going to release when he files in April. You know, that’s going to be personally up to him. My practice has been all along is, I release my tax returns every year as soon as they are filed. And that would be my preference.

LAUER: The appearance here is you wait until April, the nomination would be secured by that time and you don’t have to worry about fallout in the primaries.

CHRISTIE: Well, listen, I think he already started to speak about it yesterday, about the rate he pays. What I would say to Governor Romney is: if you have tax returns to put out, um you know, you should put them out. You put them out sooner rather than later because it’s always better in my view to have complete disclosure, especially if you’re the frontrunner.

Christie also said something very similar on MSNBC’s “Morning Joe” this morning.

This is what’s generally referred to as “off message.” Romney has said repeatedly that he does not intend to release these materials. As recently as a couple of weeks ago, the former governor said he’d “consider” releasing his tax returns “if I become president.” (In other words, after the election Romney might do what every other modern candidate has done before the election.)

And yet, here was Romney’s top surrogate arguing on national television that Romney should stop hiding his tax returns from the public. This is not at all what I expected.

On a related note, reader R.L. noted that Romney told reporters yesterday that “people will want to see the most recent year” of tax returns. He is, in other words, already trying to set a very low bar — Romney apparently intends to wait until after he’s the GOP nominee, then maybe release his returns for just a single year.

That won’t do. Barack Obama released nearly a decade’s worth of tax returns in 2008. When George Romney ran for president, he released 12 years of returns. Disclosure for one year won’t exactly meet any fair standard for transparency.

We’re talking about information the public deserves to know. Paul Krugman added this morning, “[A]re we sure that his tax rate is even as high as 15 percent? How much is shielded in tax havens? We need the returns.”

As of this morning, the pressure of Romney has been ratcheted it up considerably.

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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.