Republicans eagerly elected Rep. Mike Johnson as House speaker on Wednesday, elevating a deeply conservative but lesser-known leader to the seat of U.S. power and ending for now the political chaos in their majority.

Rep. Johnson, 51, of Louisiana, swept through on the first ballot with support from all Republicans anxious to put the past weeks of tumult behind them and get on with the business of governing. He was quickly sworn into office.

“We are ready to get to work again,” he said after taking the gavel.

To the American people watching he said, “Our mission here is to serve you well and to restore the people’s faith in this House.”

A lower-ranked member of the House GOP leadership team, Rep. Johnson emerged as the fourth Republican nominee in what had become an almost absurd cycle of political infighting since Kevin McCarthy’s ouster as GOP factions jockeyed for power. While not the party’s top choice for the gavel, the deeply religious and even-keeled Rep. Johnson has few foes and an important GOP backer: Donald Trump.

“I think he’s gonna be a fantastic speaker,” Mr. Trump said Wednesday at the New York court- house where the former president, who is now the Republican front-runner for president in 2024, is on trial over a lawsuit alleging business fraud.

Three weeks on without a House speaker, the Republicans have been wasting their majority status — a maddening embarrassment to some, democracy in action to others, but not at all how the House is expected to function.

Far-right members had refused to accept a more traditional speaker, and moderate conservatives didn’t want a hard-liner. While Rep. Johnson had no opponents during a private party roll call late Tuesday, some two dozen Republicans did not vote, more than enough to sink his nomination.

But when GOP Conference Chair Rep. Elise Stefanik rose to introduce Rep. Johnson’s name Wednesday as their nominee, Republicans jumped to their feet for a standing ovation.

“House Republicans and Speaker Mike Johnson will never give up,” she said.

Democrats again nominated their leader Rep. Hakeem Jeffries of New York, criticizing Rep. Johnson as an architect of Mr. Trump’s legal effort to overturn the 2020 presidential election he lost to President Biden.

With Republicans controlling the House only 221-212 over Democrats, Mr. Johnson could afford just a few detractors to win the gavel. He won 220-209, with a few absences.

Rep. Jeffries said House Democrats will work with Republicans whenever possible for the “good of the country.”

Overnight the endorsements for Rep. Johnson started pouring in, including from failed speaker hopefuls. Rep. Jim Jordan, the hard-charging Judiciary Committee chairman, gave his support, as did Majority Leader Steve Scalise, the fellow Louisiana congressman, who stood behind Rep. Johnson after he won the nomination.

“Mike! Mike! Mike!” lawmakers chanted at a press conference after the late-night internal vote, surrounding Rep. Johnson and posing for selfies in a show of support.

Anxious and exhausted, Republican lawmakers are desperately trying to move on.

Rep. Johnson’s rise comes after a tumultuous month, capped by a head-spinning Tuesday that within a span of a few hours saw one candidate, Rep. Tom Emmer, the GOP Whip, nominated and then quickly withdraw when it became clear he would be the third candidate unable to secure enough support from GOP colleagues after Mr.Trump bashed his nomination.

“He wasn’t MAGA,” said Mr. Trump, referring to his Make America Great Again campaign slogan.

Attention quickly turned to Rep. Johnson. A lawyer specializing in constitutional issues, Rep. Johnson had rallied Republicans around Mr. Trump’s legal effort to overturn the 2020 election results.

Elevating Rep. Johnson to speaker gives Louisianians two high-ranking GOP leaders, putting him above Rep. Scalise, who was rejected by hard-liners in his own bid as speaker.

Rep. Johnson is affable and well liked, with a fiery belief system, and colleagues swiftly started giving him their support.

“Democracy is messy sometimes, but it is our system,” Rep. Johnson said after winning the nomination. “We’re going to restore your trust in what we do here.”