Republican Debate in Arizona: LIVE COVERAGE
Former Pennsylvania Sen. Rick Santorum, former Mass. Gov. Mitt Romney, Texas Rep. Ron Paul and former House Speaker Newt Gingrich face off tonight in Arizona for their last primary debate before Super Tuesday. Click here for live coverage of the debate, hosted by CNN, with minute-by-minute updates. REUTERS

The Republican presidential candidates have held nearly two dozen debates during the campaign season, but CNN may have proposed one too many.

The network canceled its March 1 debate ahead of the March 6 Super Tuesday, where 10 states will hold primary contests.

Mitt Romney and Ron Paul backed out Thursday, citing busy campaign schedules. Rick Santorum followed suit, leaving Newt Gingrich, whose love for debates is well-known, the only candidate willing to participate in the nixed event.

Without full participation of all four candidates, CNN will not move forward with the Super Tuesday debate, CNN said in a statement.

Romney's camp said in a statement the former Massachusetts governor will be spending his time before Super Tuesday in Georgia and Ohio.

With eight other states voting on March 6, we will be campaigning in other parts of the country and unable to schedule the CNN debate, said Romney spokeswoman Andrea Saul.

Debate Cancellation Hurts Gingrich

Meanwhile, one less debate is surely a blow to Gingrich. The former House speaker has embraced the events, owing his key South Carolina primary victory to solid and aggressive debate performances. He has even invited President Barack Obama and Romney to hours-long Lincoln-Douglas-style debates. Gingrich did, however, get former hopeful Jon Huntsman to participate in the hours-long debate,

When told that Romney had backed out of CNN's March 1 debate, Gingrich said Romney wanted to avoid confronting his rivals.

The Romney model is to go to Wall Street and raise huge amounts of money to run negative ads, Gingrich told The New York Times while campaigning in Los Angeles, and you can understand why having to defend that strategy is probably not something he's very happy with.

Still, there will be a chance for the Final Four to face off before a national audience at CNN's Feb. 22 debate in Mesa, Arizona, the network said.