Republicans rallied behind a new standard-bearer on Wednesday as the US House of Representatives elected its 56th speaker -- ending weeks of turmoil and bitter infighting that has paralyzed Congress in a period of international and domestic crisis.

Mike Johnson, a staunch ally of Donald Trump who spearheaded legal efforts to overturn the 2020 presidential election, received the unanimous support of his party to lead the lower chamber of Congress, which has been at a standstill since Kevin McCarthy was ousted in a right-wing coup on October 3.

The Louisiana congressman was the fourth Republican picked by his party in three weeks to replace McCarthy, but the only nominee to garner enough support on the House floor, where he received several standing ovations from his colleagues.

"This House Republican majority is united," Johnson had told reporters as colleagues cheered and applauded following his nomination.

A virtual unknown, Johnson's lack of star power appears to have helped the 51-year-old attorney and religious rights campaigner, who lacked the enemies from his own side that prompted the downfall of every other candidate.

Far from his party's first choice, he was able to capitalize on the desperation of lawmakers to move on from the impasse, although winning the gavel was still a heavy lift in the deeply-fractured House Republican Conference.

"I haven't heard one negative comment about him. Everybody likes him, he's respected by all... somebody that's going to be really spectacular and maybe for many years to come," Trump said ahead of the vote.

Formerly a junior member of the leadership as the conference vice chairman, Johnson entered the House of Representatives in 2017, having stirred controversy with legislation seen as anti-gay in Louisiana state politics.

The married father of four also voted against codifying federal protections for same-sex marriage last year.

He was the ringleader among more than 100 Republicans who signed onto a legal brief supporting a lawsuit seeking to overturn the 2020 election results in four swing states won by President Joe Biden. (AFP)