Mitt Romney and Rick Santorum will take the stage Wednesday night for their first meeting since Santorum upended the GOP race two weeks ago with a spate of victories over the Republican front-runner.

The hugely anticipated presidential debate offers the GOP hopefuls their last, best chance to reclaim control of a chaotic race before a tidal wave of make-or-break contests on Super Tuesday, March 6.

For Santorum, the Arizona and Michigan primaries seven days hence offer a chance to shatter Romney. A loss by Romney in either state, and especially in both, on Feb. 28 would likely plunge the Republican establishment into panic.

Romney’s task is to stop Santorum’s recent surge and reassert himself as the inevitable nominee-in-waiting who can best lead the general-election fight to unseat President Obama.

For Newt Gingrich and Ron Paul, the Arizona debate Wednesday night is a crucial opportunity, perhaps the last one, to prevent the GOP primary from becoming a two-man race that doesn’t include them.

The 19 debates that dotted the early months of the primary calendar left many crying overkill. But the four remaining candidates haven’t been onstage together since Jan. 26 — the longest span without a debate since June 2011 —leaving an unscratched itch that one GOP strategist dubbed “debate withdrawal.”

As the 2012 race has shown repeatedly, a lot can happen in a month. When the candidates last met onstage in Florida, Gingrich had just crushed Romney in South Carolina and taken the lead in national polls. In the month since, Romney squashed Gingrich’s gains with wins in Florida and Nevada, then had the rug pulled out from under him days later by Santorum, who handed him defeats in Minnesota, Missouri and Colorado.

Romney regained his footing with a narrow win in Maine, but Santorum has surpassed him in national polls and is even leading in Michigan, a must-win state for Romney where he and his family have deep ties.

But while Romney was able in Florida to bury Gingrich — then his top rival — with millions of dollars of ads that drove up Gingrich’s negative ratings, he has run out of obvious ammunition to use against Santorum.

Santorum lacks the heavy personal and ethical baggage that made Gingrich an easy target. Romney’s campaign has fired up its surrogates and ad machine, but the attacks have centered on Santorum’s past support for earmarks, circuit court judicial appointments and voting rights for ex-felons.

It was easy to move the needle with attack ads on a candidate tied to Freddie Mac, lobbying and ethics charges, but, as Romney’s campaign has learned, more difficult to do it with murky issues like earmarks.

Adding to Romney’s difficulties is his inability to use the most potent argument against Santorum: that his social conservatism makes him unelectable.

Santorum has spent the past few weeks cheerfully embracing his role as a culture warrior, marching to the right on contraception coverage, accusing Obama of employing a theology “not based on the Bible” and questioning the science of global warming.

That has some Republican insiders publicly fretting the party’s fate if Santorum is the nominee, but has left Romney in a weak position to undercut him.

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