"The will be no loud bells," CNN debate moderator Wolf Blitzer said, introducing the set-up. "No flashing lights."

No flashing lights, that is, except the twinkling of Hillary Clinton's eye. Clinton is back in business, and she's feeling fine. "This pantsuit is asbestos tonight," she joked, replendent in a trendy grey jacket and black shirt. "This has to be a big election. This is going to be one of the most important elections we've had in this country."

Obama opens with a prefatory compliment then swings at his chief rival: "Senator Clinton is a capable person and she has run a terrific campaign...what the American people are looking for right now is straight answers to tough questions." With regard to Clinton and immigration question, it took her "two more weeks" after the last debate "until we could get her answer on what her position was."

Clinton returns fire with detailed policy fire -- her forte. "I hear what Senator Obama is saying, and he talks a lot about stepping up and taking strong positions....his [healthcare] plan would leave 15 million people out. That's about the populations of Nevada, Iowa, New Hampshire and South Carolina."

Obama tries to return fire: "I do provide universal healthcare...She thinks the problem for people without healthcare is that no one has mandated, has forced them to have healthcare."

Something is happening in the audience, that Obama is responding to, but no one watching CNN can hear it. "Hillary, she states that she wants to," he says, looking distracted. "She is not enforcing this mandate."

Blitzer tosses it over to Edwards, who opens by declaring, "Nobody on this stage is perfect," before launching into his stump critique of Clinton, her voting with Bush and Cheney and the neocons on Iran, and her corruption.

Clinton hits back and puts him on the defensive, pointing out that she's got a long track record, while Edwards was not for universal health coverage when he ran for president in 2004. Then she takes him on directly.

"When someone starts throwing mud," she says, the least we can do is make sure "it's accurate and not out of the Republican playbook."

"For him to be throwing this mud and throwing these charges really retracts from what we are trying to do for America."

Whatever was going on over the past few weeks with Sen. Clinton now looks like a minor blip -- a change in the weather cold, rather than a sign of any deeper weakness. She's back to herself, and back to being in fine form. The tone for the rest of the debate is set.

--Garance Franke-Ruta