“I don’t care if he lies or exaggerates in his tweets or breaks his vows to his wife, so long as he keeps his promises to me,” Leah Rownan, a self-described social conservative from Henderson, Nev., told The Times, citing the economy and Mr. Trump’s Supreme Court nominations as decisive for her vote. “And he has.”

Many of Mr. Trump’s supporters also said they felt vindicated by the conclusions of Robert Mueller’s report on Russia’s interference in the 2016 election. While the former F.B.I. director painted a damning portrait of a campaign that was riddled with Kremlin sympathizers and a candidate whose real-estate ventures were beholden to Russian investors, no clear evidence of collusion between Mr. Trump and Moscow ever emerged and the president was never indicted.

“It was always a red herring, just like Trump said,” said Bernard Schwartz, a gun store owner from Houston, Tex. “Democrats wasted a lot of ammo on that one.”

Democrats also failed to capitalize on, and may have been damaged by, winning back control of the House of Representatives, but not the Senate, in the 2018 midterms. Mr. Trump proved effective, if characteristically vitriolic, in making a foil of the House speaker, Nancy Pelosi. Efforts to impeach the president mainly served to energize his base. Polling surveys suggested that wavering voters saw a Democratic Party more invested in humiliating the president than in helping them.

As is often the case in losing presidential campaigns, it did not take long for campaign aides to Senator Warren to offer damning appraisals of her performance as a candidate. Historical references abounded: The Children’s Crusade; Pickett’s Charge; the McGovern campaign of 1972. The common thread was that the campaign’s moral fervor repeatedly got the better of its message focus.

“Trump succeeded,” lamented one moderate former Democratic lawmaker who asked to speak on background. “He got my party to lose its marbles.” The lawmaker cited calls by party activists to abolish the U.S. Immigration and Customs Enforcement agency — calls the Warren campaign did not formally endorse but did little to refute — as emblematic of the party’s broader problems.

“What do Democrats stand for?” he asked. “Lawlessness or liberality? Policymaking or virtue signaling? Gender-neutral pronouns and bathrooms or good jobs and higher wages?”

As is his way, Mr. Trump wasted little time rubbing salt into Democratic wounds. “Democrats used to stand with the Working Man,” he tweeted Wednesday morning. “Now it’s the party of Abortion and Amnesty. All that’s missing is Acid. Sad!”

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