WASHINGTON (Reuters) - President Donald Trump calls one of the top contenders to take over leadership of the U.S. House of Representatives next year “my Kevin” and frequently attacks the other, Nancy Pelosi.

FILE PHOTO: House Democratic leader Nancy Pelosi (L) and Speaker of the House Paul Ryan (R), meet with U.S. President Donald Trump in the Oval Office of the White House in Washington, U.S., December 7, 2017. REUTERS/Kevin Lamarque/File Photo

Both Republican Kevin McCarthy and Democrat Pelosi are mainstream California politicians, but the contrast between the two is stark, as congressional elections near on Tuesday.

Americans will vote for candidates for all 435 House seats with the outcome setting the tone for Trump’s 2019-2020 relations with Congress. Whichever party captures the most seats will choose the next House speaker, who sets the chamber’s legislative and political agendas.

Republicans are fighting to defend their House majority, while Democrats seek to snatch it by gaining at least 23 more House seats. Polls show Democrats are favored, but some races were close in the final days of campaigning.

The stakes are high for Trump, who has been largely supported by Republicans under Speaker Paul Ryan’s rule. That would change if Democrats took over, said lawmakers, aides from both parties and strategists.

In a Democratic House, Pelosi, the party’s leader in the chamber for 16 years, would likely become speaker. The San Francisco liberal made history in 2007-2011 as the first woman to hold the job.

Trump mocked Pelosi in August, saying she has “every right to take down the Democrat Party if she has veered too far left.” Many Republican campaign ads target her.

If Pelosi took the gavel, Democratic-led committee investigations of Trump, his tax returns, his family and his administration would follow.

‘MINIMALLY ENTHUSIASTIC’

Slideshow ( 3 images )

Pelosi has revealed a liberal legislative agenda starting with changes to campaign finance law to encourage more small donations. “Put me down for minimally enthusiastic about that,” Senate Majority Leader Mitch McConnell told Reuters in an October interview.

Another idea rankling Republicans - raising the federal minimum wage - would be high on Pelosi’s agenda.

But Pelosi, with a record of bipartisan achievement, has recently promoted two legislative projects that might appeal to Trump: bills cutting prescription drug prices and spending more on infrastructure. Trump ran for president in 2016 touting both ideas.

So, a Democratic “blue wave” victory putting Pelosi, 78, back in power would spell trouble for Trump in some ways but perhaps opportunity in others, analysts said.

Meanwhile, a narrow majority could embolden a Pelosi challenge from Democrats seeking younger leadership.

A spokesman for Pelosi referred questions to previous comments by the Democratic leader.

Pelosi deflected prospects of an intraparty struggle. “None of that frightens me. It’s what I anticipate, what I expect and what I thrive on,” she declared at a mid-October Harvard University forum.

With no declared adversary yet, one House Democratic leadership aide predicted Pelosi could weather a challenge: “I would love for someone to tell me who could do as good of a job running a slim majority in the age of Trump.”

Jim Manley, a Democratic strategist, noted “pent-up demand” for a leadership change. He added, “I’ve learned a long time ago never to bet against Leader Pelosi.”

REPLACING RYAN

The other scenario for Trump has Republicans maintaining their majority, raising questions of who would succeed retiring Speaker Ryan. He is promoting No. 2 House Republican McCarthy. In 2015, McCarthy’s first bid for speaker was torpedoed by fractious Republican conservatives.

Trump has a close relationship with McCarthy, a former deli owner. “My Kevin,” as Trump sometimes calls him, has offered legislation to fully fund the president’s proposed U.S.-Mexico border wall.

But conservative rivals are keeping close watch on whether McCarthy’s bid for speaker takes flight. No. 3 House Republican Steve Scalise said he would not challenge McCarthy. But supporters of Scalise, the Louisianan who was shot in 2017 by a lone gunman, have said he would jump in if McCarthy sputters.

Aides to McCarthy did not respond to requests for comment.

Jim Jordan, a leader of the right-wing House Freedom Caucus, has announced his candidacy for speaker, complaining that Republican leaders are too apt to back down from fights with Democrats. Jordan has occasionally opposed some Trump-favored legislation.

Jockeying for the speaker’s job will intensify in mid-November as newly elected Republican and Democratic House members prepare to choose respective leaders. In early January, all 435 House members will vote for a speaker.