By Susan Cornwell

WASHINGTON (Reuters) - Nancy Pelosi may face a challenge to her 14-year-old role as the leading Democrat in the U.S. House of Representatives now that Republicans have captured the White House and maintained their grip on Congress.

Representative Tim Ryan, 43, of Ohio, is weighing a run against Pelosi, 76, who is the House minority leader and former speaker of the House, said Ryan's spokesman Michael Zetts. The party vote for minority leader is scheduled for Thursday.

"He is concerned that if changes aren't made we will be in the political wilderness for many years to come," Zetts said. It was unclear how much support Ryan might have. He has been in the House since 2003.

Voters who elected Republican Donald Trump over Democrat Hillary Clinton on Nov. 8 also gave Democrats a few more seats in the 435-member U.S. House of Representatives and the 100-member Senate, but Republicans held on to their majorities in both. Democrats had expected to do much better; some had predicted double-digit wins in the House.

Pelosi, of California, faced calls from Representative Seth Moulton and other Democrats, dismayed by the election results, to postpone the party's leadership election until later in November while a reassessment is made.

House Majority Leader Kevin McCarthy, a Republican, may have given some ammunition to Pelosi's detractors on Monday when he said, "I kind of like Pelosi staying around. As long as she’s there, I think we stay in the majority."

The new Congress convenes on Jan. 3; Trump will succeed President Barack Obama, a Democrat, on Jan. 20. In the U.S. Senate, New York's Chuck Schumer is expected to replace the retiring fellow Democrat Harry Reid as minority leader.

In the Republican party, no one is challenging Senate Majority Leader Mitch McConnell, and House Republicans are expected on Tuesday to nominate Paul Ryan to remain House speaker.

Ryan would face an election in January, when all members of the new House, both Democrats and Republicans, vote on a new speaker.

Before Trump's win, some Republican conservatives angered by Ryan's tepid support for Trump were talking about trying to block his re-election. Those threats have subsided but not vanished.

An aide to New York Republican Representative Chris Collins said, "Congressman Collins fully believes Speaker Ryan is a slam dunk to be re-elected as speaker, and looks forward to working with him in the next Congress." Collins was Trump's first supporter in the House.

Some conservative Republicans still have doubts. "Presently Speaker Ryan does not have my vote, but I will listen to his message tomorrow," Representative Tom Massie of Kentucky said in a statement.

(Editing by Kevin Drawbaugh and Howard Goller)