Post-Super Tuesday, Obama's former campaign chief calls Biden a 'clear front-runner'

The question that remains: Can Joe Biden maintain momentum in his comeback?

After calling the Democratic presidential primary a two-person race over the weekend, David Plouffe, Obama's former campaign manager, said Super Tuesday's results show former Vice President Joe Biden as the "clear front-runner."

"He is now the clear front-runner just because in a delegate situation, he's got a lot more states to come where he's likely to win by big margins, which is how you win delegates," Plouffe told "Powerhouse Politics". "[Vermont Sen.] Bernie Sanders will win some states, but it's hard to see a place where he's going to win 2-to-1."

Recent developments have played into Biden's favor -- from a coveted Democratic endorsement by influential Rep. Jim Clyburn to a successful South Carolina primary win, and significant endorsements by former 2020 presidential candidates: Minnesota Sen. Amy Klobuchar, former South Bend, Indiana Mayor Pete Buttigieg, and just on Wednesday, former New York City Mayor Mike Bloomberg.

Those close to the Obama administration have also come out with their support for the former vice president over the past week, such as former National Security Adviser Susan Rice and former United Nations ambassador Samantha Power.

"It's always easier in politics to get back support you once had than that you never had," Plouffe told the hosts, adding "He has one good primary night, a great one gets the Clyburn endorsement, gives a good speech. His rivals then come off the sidelines and that sends a message to everybody who had been with him."

ABC News' poll results show that Biden had significant victories in South Carolina and at least 10 of the Super Tuesday states. Plouffe said the message that has emerged from those victories: "It's time to jump back into the boat ... with Joe Biden."

When asked by ABC News Political Deputy Director MaryAlice Parks about his former boss's hand in impacting the race, Plouffe denied that former President Barack Obama pulled any strings.

"No," he told Parks. "I mean, I by the way, I love all this talk about the Democratic establishment. I've worked in politics for a long time. I'd like to meet this so-called Democratic establishment."

Still, the question that remains is whether the former vice president can maintain momentum in his comeback.

"You know, it's interesting to me because it's not like Biden has been a superstar performer," he said. "He's been good since Saturday night, had a couple better debates. And I think my question is, can he continue to do that?"

He added, "My suspicion is -- knowing him a little bit -- is he's going to feel a great deal of responsibility not to let down all the people now that are throwing all of the chips into his boat."

Plouffe suggested that the upcoming debate on March 15th will be a chance to test Biden's trajectory moving forward, as it could essentially be down to two people: Biden and Sanders.

"I've seen him be a good debater. But, you know, that was a long time ago," he told the hosts. "He hasn't shown that in a multi-candidate field. So, you know, that debate's going to be a real test."

He noted that a two-person debate is much different than having five or six candidates, adding that he hopes it is tough in order to better prepare the Democratic candidates for what's up ahead.

"I am not one that's worried about the race getting tough because ultimately what's looming on the other side is the Trump monster," Plouffe said. "And, you know, he's going to be seven times harder than anybody in the primary field was to deal with."

With the way the rest of the 2020 race will play out, he still projected that Biden could win by large margins in upcoming states.

"I think it's going to come down to a lot of people on the ground honestly doing the right thing. And the winner has to be super gracious."

When ABC News Political Director Rick Klein asked Plouffe what percentage of likelihood he would assign to Biden winning the nomination, Plouffe said he did not know about a percentage but that "it's his race to lose."

"I think that in reality, Joe Biden is in a commanding position, assuming he can capitalize on it," he told Klein.

Plouffe brought up the upcoming primaries in battleground states -- such as Georgia, Florida and Mississippi -- stating Biden should not have a problem winning by a large margin. However, if he doesn't, the Democratic presidential race will be closer and longer, he said.

"I think securing his position in the race ... he's got to perform well. And so far, the last few days have been good," he added. "But, you know, he's got to prove that day in and day out."

Plouffe, who also served as Obama's White House senior adviser, authored two recently published books: "A Citizen's Guide to Defeating Donald Trump" and "Ripples of Hope"

The central message in both books is to defeat President Donald Trump in any simple way, one of which includes unifying behind whoever is the Democratic nominee, he said.

"Let's say Biden is the nominee and you were a volunteer leader for him in Michigan. Well, you need to talk to the Bernie Sanders' people involved in that campaign and say, 'You're welcome here and I want to hear your concerns'," Plouffe said.

Although he acknowledged this won't automatically happen overnight, Plouffe urged voters to seriously consider backing whoever is the potential Democratic nominee, in order to defeat Trump.

"I think unification will not be at the top of the list, but it could be a pretty important contributing factor," he added.

Powerhouse Politics podcast is a weekly program that posts every Wednesday, and includes headliner interviews and in-depth looks at the people and events shaping U.S. politics. Powerhouse Politics podcast is hosted by ABC News Chief White House Correspondent Jonathan Karl and ABC News Political Director Rick Klein. Special thanks to ABC News Deputy Political Director MaryAlice Parks, who joined this week as a guest host.