Newt Gingrich has been suggesting for some time that other Republican presidential primary opponents should drop out of the race so he can consolidate support as the anti-Romney candidate. Texas Governor Rick Perry dropped out and gave Gingrich his endorsement just as the former Speaker was picking up steam before his South Carolina GOP primary win, and Gingrich once again suggested that Rick Santorum step aside in the days leading up to the Florida GOP primary.

Santorum has stood his ground, and is now fighting back.

Following Gingrich‘s distant second place finish to Mitt Romney in Florida’s GOP primary Tuesday, a state where Santorum secured 13 percent of the vote after applying considerably less time and resources, the Pennsylvania senator has responded that Newt is the one who should back down.

“If you don’t want Mitt Romney, obviously Newt Gingrich doesn’t have what it takes to win this,” Santorum told reporters from Las Vegas Tuesday night as Florida’s results projected Gingrich far behind Romney. “Let’s give someone else a shot.”

“In Florida, Newt Gingrich had his opportunity,” POLITICO reports Santorum told supporters Tuesday. “He said, ‘I’m going to be the conservative alternative.’ … It didn’t work. He became the issue. We can’t allow our nominee to be the issue in the campaign.”

Santorum’s attack against Gingirch went a step further Wednesday, when his campaign began airing a new Television ad in Nevada which aligns the former Speaker with President Obama and Rep. Nancy Pelosi.

The National Journal’s Tim Alberta writes that the Santorum campaign noticeably spares the newly invigorated Republican front-runner Mitt Romney:

“That Santorum would spare Romney from such an effective, well-orchestrated attack is puzzling. After all, Romney has been criticized for previously supporting these policies — cap and trade, amnesty, insurance mandates and bailouts — at various points during his two presidential campaigns. Indeed, some of those attacks have been leveled by Santorum himself. So why did the former Pennsylvania senator, who was forceful last week in tying Obama’s policies to Romney and Gingrich, choose not to kill two birds with one stone in this major post-Florida media buy?

In short, because Santorum‘s most pressing priority isn’t taking down Romney — it’s emerging as the consensus conservative alternative to him. And in order to do that, Santorum must first displace Gingrich — both in the polls and in the media narrative — as Romney’s main rival.”

The Santorum strategy and Alberta’s analysis further exemplifies what has always been the overall rider of the 2012 GOP primary: there are two candidates; Romney and whoever claims the Anti-Romney mantel.