Watch the last presidential debate before Super Tuesday: CNN's Arizona Republican Debate on Wednesday at 8 p.m. ET.
Washington (CNN) -- In no particular order, here are four things you should watch in this week's desert debate: Ron Paul, Rick Santorum, Mitt Romney, Newt Gingrich.
The final four have not shared a stage in almost a month: Not since Romney won Florida, Nevada and Maine. Not since Santorum triumphed in Minnesota, Missouri and Colorado. Not since Paul won -- well, Paul won nowhere, though he told me on CNN's "State of the Union," "It all depends on how you measure winning. ... The bottom line is who is going to get the delegates ... and we think we're doing pretty good."
Also not winning anywhere since the last debate is Gingrich, who retains his down-but-never-out storyline. The former House speaker promised recently, "I have been front-runner twice. I suspect I'll be the front-runner again in a few weeks."
It is at least arguable that since the last debate on January 26, Gingrich has faded and Paul has hit a ceiling. Still, all four Republican presidential hopefuls have jointly suffered from an increasing Republican anxiety about the field.
The latest CNN/ORC poll, conducted a week ago, shows 55% of Republicans are satisfied with their presidential candidates, down 11 points from October 2011.
Arizona's debate matters.
It could be an oasis for Gingrich's regularly in-debt campaign, providing an audience of millions for the price of a plane flight and a hotel room. Debates are usually terra firma for Gingrich, who has an instinct for the jugular and a way of channeling the anger and frustration of the Republican right. His assaults on the media and on President Barack Obama have regularly drawn sustained applause and sometimes standing O's from debate audiences.
More importantly, they have provided the day-after headlines that have fueled the Gingrich campaign.
But the dynamic is different now. The time is later, and much as Santorum once needed Gingrich to falter so he could step in, Gingrich needs Santorum to collapse under the weight of expectations for a front-runner.
There isn't much room for error at the top of a pyramid, and the Arizona debate is the first time Santorum will take the center position on stage where the front-runner stands and gets pummeled.
Gingrich is not the only one looking to push Santorum -- Paul is traveling to Arizona loaded for bear and offered me what might be a preview of his intent for the debate.
Paul said he doesn't think it's possible for Santorum to beat Obama this fall. Expressing impatience with this past week's brouhaha over birth control, he accused Santorum of "pretending" to be a conservative. Rather, Paul said, Santorum has been liberal in all the things he's voted for and added that he has an "atrocious" voting record.
Still, like the most recent debates, angst is likely highest for the "sometimes" front-runner, the "almost" front-runner, the "weak" front-runner -- Romney.
Because of his cash on hand and his sturdy operation, Romney is still pundits' odds-on favorite to win. Now though, he is in danger of losing his home state of Michigan, which along with Arizona holds its primary a week from Tuesday.
He told the Grand Rapids Press editorial board that a Romney loss in Michigan is "not going to happen."
Numerically, he could lose Michigan and still win the nomination, but the optics of failing in his home state would raise uncomfortable questions. If he cannot connect there, if he cannot connect now, where and when will he?
Romney remains a man in search of his own passion or at least a man in search of a way to convey it.
The stakes are enormous on Wednesday -- not only because there's been no debate during a month of change in the race, but also because no more are scheduled before Super Tuesday in early March, when 10 states hold caucuses or primaries.
For Gingrich and Paul, Santorum and Romney, the Arizona debate may be the last chance to make another impression.