Tonight, CNN and the Congressional Black Caucus Institute host the final Presidential Debate before the South Carolina Democratic Primary. Sen. Hillary Clinton, former Sen. John Edwards, and Sen. Barack Obama will take the stage in Myrtle Beach. Tune into CNN and http://www.CNNPolitics.com throughout the day for extensive coverage of this event, as well as the race for the Republican presidential nomination. CNN’s Wolf Blitzer will moderate with questions from CNN’s Suzanne Malveaux and Joe Johns. The Debate will air live from 8 p.m. ET to 10 p.m. ET. Democratic Debate Day

WASHINGTON (CNN) — He’s not on the ballot this cycle, but it wouldn’t be a big surprise to see former President Bill Clinton take the stage with the remaining Democratic presidential contenders at tonight’s CNN/Congressional Black Caucus Institute debate in South Carolina.

The former president was nearly as much of a presence leading up to Saturday’s Nevada caucuses as his wife, Sen. Hillary Clinton – or any of the Democratic candidates, really. In Nevada, as in New Hampshire, President Clinton was in a fighting mood the night before the vote, taking direct aim at Sen. Barack Obama; and again, in defiance of the polls, his wife pulled out a win.

This time, Obama is calling foul. President Clinton may not be a candidate this year, Obama told ABC, but he’s starting to feel as though he’s “running against both Clintons.” Top Obama strategist David Axelrod is chiming in too, accusing the couple of a “good cop, bad cop” routine this campaign season.

There may be no method to this madness, but there’s certainly a routine developing in the Clinton-Obama feud: Public truces are made, then broken hours later; last-minute, dueling conference calls are scheduled an hour or so apart; escalating charges and counter-charges are traded, investigations called for, inboxes flooded with allegations of distortion and dirty tricks. The over-under on response time from either side, in a Sunday CNN calculation, is down to a mind-warping seven minutes.

And as shock waves from the chaotic Nevada caucuses continue to ripple through Democratic ranks, yet another unwelcome pattern seems to be repeating itself. Last week, during the dustup over Sen. Clinton’s comments on Dr. Martin Luther King Jr.’s legacy, observers noted that her campaign stood to benefit every time race was on the table, no matter the context.

This week, Obama may have the most to gain from the emerging dynamic: African-American voters in South Carolina have been swinging his way, according to recent polls – and nothing motivates the base quite like the charges of voter suppression coming out of Nevada. Both the Clinton and Obama campaigns are accusing the other of engaging in the practice.

The brutal bloodletting of the primary season may disappear quickly after a nominee is decided. But will the battle wounds really heal completely by November?

Momentum seems to have a short shelf life this cycle, but for what it’s worth, two Republicans come out of Saturday’s vote with the wind at their backs. John McCain won the kingmaker South Carolina contest, eight years after his campaign collapsed there. And Ron Paul’s second-place showing in Nevada’s neglected GOP caucuses – and near-tie with third-place Fred Thompson in South Carolina – may, at least for the moment, silence the skeptics. (Could it be the blimp?)

The list of walking wounded out of South Carolina is longer. It includes: Mike Huckabee, who actually split the state’s evangelical vote with John McCain; Fred Thompson, whose last-stand heroics translated into an underwhelming 16 percent finish; and Rudy Giuliani, whose Florida focus reduced his Saturday showing there to an asterisk.

Somewhere in the middle: Mitt Romney, who comes out of the weekend with a delegate lead, a caucus win – and a disappointing fourth-place showing in South Carolina, despite spending as much on ads there as the rest of the Republican field combined.

– CNN Associate Political Editor Rebecca Sinderbrand