CLEVELAND — Republican President Donald Trump and Democratic rival Joe Biden battled fiercely over Trump’s leadership on the coronavirus pandemic, the economy and the integrity of November’s election in a chaotic first debate on Tuesday marked by personal insults, name calling and Trump’s repeated interruptions.

Moderator Chris Wallace never established control of the debate. The two White House contenders talked over each other and lobbed insults in a breathtaking political brawl that made it hard for either to make a point.

“Will you shut up, man? This is so unpresidential,” said an exasperated Mr. Biden after Mr. Trump’s repeated interruptions during the first segment of the debate on the Supreme Court.

Mr. Biden later called Mr. Trump a “clown,” a “racist,” and “Putin’s puppy” in reference to Russian President Vladimir Putin and told Mr. Trump: “You’re the worst president America has ever had.”

Mr. Trump for his part said: “There’s nothing smart about you, Joe.”

Late in the debate, Mr. Wallace himself urged the president to stop his interruptions.

Mr. Biden, 77, has held a consistent lead over Mr. Trump, 74, in national opinion polls, although surveys in the battleground states that will decide the election show a closer contest. It was hard to determine whether the debate would move the needle.

Mr. Biden questioned Mr. Trump’s leadership on the coronavirus pandemic, which has killed more than 200,000 Americans, saying Mr. Trump had panicked and failed to protect Americans because he was more concerned about the economy.

“He panicked or he looked at the stock market,” Mr. Biden said of Mr. Trump, who has pushed for states to reopen their economies and played down the threat of the pandemic.

“A lot of people died and a lot more are going to die unless he gets a lot smarter, a lot quicker,” Mr. Biden said.

Mr. Trump objected to Mr. Biden using the word “smart.”

“You graduated either the lowest or almost the lowest in your class. Don’t ever use the word smart with me. Don’t ever use that word,” Mr. Trump said.

He defended his approach on the pandemic and said “we have done great job.”

“But I tell you, Joe, you could never have done the job we’ve done. You don’t have it in your blood,” he said.

With more than a million Americans already casting early ballots and time running out to change minds or influence the small sliver of undecided voters, the stakes were enormous as the two White House candidates took the stage five weeks before the Nov. 3 Election Day.

The two contenders did not shake hands as they entered the debate, adhering to protocols on social distancing because of the coronavirus.

Mr. Trump, who has refused to commit to a peaceful transfer of power if he loses the election, repeated his unfounded allegations that mail-in voting would lead to fraud. Experts say fraud is extremely rare.

Mr. Trump said he expected the Supreme Court might have to decide the election and “look at the ballots.” He urged his supporters to go and watch the balloting.

“If I see tens of thousands of ballots being manipulated, I can’t go along with that,” he said, adding “They cheat.”

Mr. Biden urged Americans to make a plan to vote and assured voters that Trump would be gone if Biden wins. He said he would not declare victory until the outcome was validated.

“If we get the votes, it’s going to be all over. He’s going to go,” he said, adding Mr. Trump’s complaints about mail-in ballots was that Mr. Trump was “afraid” to count the votes.

“I’m concerned that any court would have to settle this,” he said. — Reuters