Former New York mayor Mike Bloomberg approached his second chance at a national debate stage Tuesday determined to live up to his campaign motto and show he could “get it done.”

“Senator! Senator!” Bloomberg interrupted as Sen. Bernie Sanders (I-Vt.) was finishing his first answer. “Vladimir Putin thinks that Donald Trump should be president of the United States. And that’s why Russia is helping you get elected — because you lose to him.”

The sudden, pointed shot across the leading candidate’s bow demonstrated just how high the stakes were for one of the richest people in the world, who finds himself fighting for his political life. After spending more than anyone in history to win the White House, Bloomberg needed to prove to Democrats that the product his ads have been selling actually exists in real life.

While falling short of the glossy image that appeared during the commercial breaks, Bloomberg succeeded in doing what he had failed to do a week earlier in Las Vegas. He delivered his messages — about his experience, his policy goals and his political focus — without a script in front of him, albeit with less polish, more stiffness and a far more stilted style of delivering a joke than his ads suggest.

“I have been training for this job since I stepped on the pile that was still smoldering on 9/11. I know what to do. I’ve shown I know how to run a country. I’ve run the city which is almost the same size — bigger than most countries in the world,” he said at one point. “I’m the one choice that makes some sense. I have the experience, I have the resources, and I have the record.”

It was an improvement by almost any measure over his debut a week earlier in Las Vegas, when he seemed to shrink from conflict, showed his nerves and spent long periods disengaged from the discussion onstage. This time he frequently raised his hand to demand more time, mostly filled the time he was allotted and pushed back aggressively against his rivals.

Howard Wolfson, the Bloomberg adviser responsible for overseeing debate preparation, joked after the debate about the turnaround when he arrived in the spin room before many other candidates.

“We went back. We watched the Seinfeld episode ‘The Opposite,’ ” Wolfson said of the shift in performance from Las Vegas. “And we did everything differently.”

Still, Bloomberg spent significant time responding to attacks — on his treatment of women, his comments about banks’ redlining policies, his yet-unreleased tax returns and his praise of the Chinese leadership. He appeared agitated when Sen. Elizabeth Warren (D-Mass.) cited a woman’s account that he told her to “kill” her baby when she got pregnant, responding: “I never said it. Period, end of story.”

It was far from clear whether his performance was enough to save his hopes for the nomination. By his campaign’s own assessment, Bloomberg and the rest of the Democratic field have a rapidly dwindling window to prevent Sanders from winning an insurmountable delegate lead on March 3, Super Tuesday, when 14 states hold primaries and Bloomberg will appear on ballots for the first time.

Sanders is on track to earn delegates in nearly every district that day, his advisers say, and is poised for a big win in the delegate-rich state of California, while most of his rivals are struggling to meet the 15 percent threshold there that is required to earn any delegates. Sanders is also polling strongly in several other Super Tuesday states.

To overcome that math, Bloomberg is attempting to reestablish himself as the electable moderate alternative to Sanders’s left-leaning, movement-driven push to change the Democratic Party. Bloomberg also needs his rival centrists in the race, particularly former vice president Joe Biden, to see their support fall in the coming weeks, a development that is unlikely if Biden, who turned in a forceful debate performance, finishes strong in the South Carolina primary on Saturday.

Bloomberg’s disappointing showing in the Nevada debate was a damaging setback for a campaign that always depended on pulling an inside straight to win. Aware that his approval and credibility had taken a hit, Bloomberg’s advisers resisted a quick turn toward more negative advertising against Sanders, which they believe will ultimately be required to prevent him from winning the nomination.

Bloomberg’s aides planned to wait until after Tuesday’s debate to decide on their advertising strategy in the days to come. If Bloomberg performed better, they reasoned, they could afford to air less positive messaging about the candidate and spend more time painting Sanders as unelectable against President Trump.

In a hint of what may be coming, the Bloomberg campaign teased a new “NOT A SOCIALIST” baseball hat on Instagram on Tuesday, with “Bring in the boss” in smaller letters on the back.

Still, Bloomberg has spent about $500 million to build a campaign that has two separate and increasingly contradictory missions. He wants to use his organization to win the Democratic nomination — and if he fails at that first goal, he plans to use the same staff, technology and bankroll to help the eventual Democratic nominee.

Bloomberg now faces the reality that the path he sees to accomplishing the first goal could undermine his ability to accomplish the second. Each of his attacks on Sanders as an unelectable radical risks sabotaging his desire to topple Trump if Sanders emerges as the nominee.

But on Tuesday he did not hold back from predicting doom if Sanders becomes the Democratic standard-bearer.

“If you keep on going,” Bloomberg warned the Democratic Party, which he rejoined in 2018, “We will elect Bernie, Bernie will lose to Donald Trump, and Donald Trump and the House and the Senate and some of the statehouses will all go red. And then between gerrymandering and appointing judges for the next 20 or 30 years, we’re going to live with this.”

Bloomberg’s rivals did not let up in their attacks, either. Warren again took the lead, accusing Bloomberg of trying to hide his finances and continuing to prevent the truth about sexual harassment settlements from becoming public. Sanders accused Bloomberg of being an apologist for China’s President Xi Jinping.

In Las Vegas last week, Bloomberg had struggled to get out responses. This time, the former New York mayor found a way to at least hit his talking points, repeating that he would release his tax returns within weeks and redirecting Warren’s focus on nondisclosure agreements.

Bloomberg recently reversed his stance on his nondisclosure agreements with three women who accused him of saying inappropriate things in the workplace. He had previously argued that it would be improper to release anyone from a contractual agreement, which he described as consensual. But shortly after the last debate, where Warren pummeled him on the issu, e he agreed to release them from the agreements.

Bloomberg had a harder time landing the jokes he had clearly prepared for his second outing.

“Let me also say,” he said at one point, in an attempt at self-deprecation, “since I have the floor for a second, that I really am surprised that all of these, my fellow contestants up here, I guess, would be the right word for it given nobody pays attention to the clock — I’m surprised they show up, because I would have thought after I did such a good job in beating them last week, that they’d be a little bit afraid to do that.”

Bloomberg will have more chances to try out his material on the road in the coming days. He has a packed travel schedule, following a CNN town hall Wednesday night, that will take him through Texas, North Carolina, Tennessee, Virginia and Alabama through the weekend, before voters offer a first verdict on his candidacy on March 3.

David Weigel in Charleston, S.C., contributed to this report.