Mitt Romney was on the campaign trail in South Carolina yesterday, and brought up the issue he expects to ride into the White House: the U.S. economy. Unfortunately for the former governor, the message isn’t quite the same as it was a few months ago.

In his remarks [Friday], Romney also acknowledged the economy was getting better — something he has said before….

“And [President Obama]’s going to say the economy is getting better,” Romney said. “Thank heavens it’s getting better. It’s getting better not because of him, it’s in spite of him and what he’s done.”

For those keeping track, Romney said twice in three sentences that he believes the economy is “getting better.”

I’ve noticed over the last week, this keeps coming up. Shortly before the New Hampshire primary, Romney said he’s “glad” the economy is improving, but quickly added that President Obama “doesn’t deserve” credit. In an interview with Bloomberg Television, Romney also said the economy is recovering, but said “this president has not helped it.”

And in a debate for the Republican presidential candidates last weekend, Romney made his case this way:

“The president is going to try to take responsibility for things getting better. It’s like the rooster trying to take responsibility for the sun rising. He didn’t do it.”

I believe campaign professionals call this a “losing argument.”

Look, I don’t know whether the recovery will strengthen in 2012. The recent evidence has been mixed; experts’ projections vary widely; and the global threats to the economy remain real and hard to predict. There is, however, room for some optimism and Romney himself believes, in his words, economic conditions are “getting better.”

But as a campaign matter, if Romney is right about a strengthening recovery, he has to realize he’s going to lose. For the entirety of 2011, the former governor had a single message he repeated ad nauseum: Obama made a bad economy worse. It wasn’t true, but so long as the recovery was largely invisible, it was a message that could fool a lot of the people a lot of the time.

Two weeks into 2012, Romney has a new message: don’t give Obama credit for making the economy better. In effect, the Republican is arguing, “Sure, Obama inherited a deep recession. And sure, he took a bunch of steps to turn the economy around. And sure, we’re now seeing more jobs being created and more economic growth. But vote against him anyway.”

This isn’t just a tough sell; it’s an impossible one.

Look again at what Romney said in last weekend’s debate: “The president is going to try to take responsibility for things getting better. It’s like the rooster trying to take responsibility for the sun rising.”

By Romney’s own reasoning, the sun is rising and it’s morning in America. As Jon Chait put it, “This seems like a shockingly weak line — if you concede that it’s morning, you’ve lost the argument.”

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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.