Battle-tested Nancy Pelosi will in all likelihood win the gavel as speaker of the House of Representatives, a dramatic return to national power for the California Democrat who made history a dozen years earlier as the first woman to lead the chamber.

She will take command during a period of American political upheaval, and with a caucus riding high after a very strong midterm election showing last November.

Thursday brings an end to Trump's one-party rule in Washington, a massive boost for Democrats who felt deflated after Trump's 2016 victory.

Progressives will be eager to push back with greater effect against an administration they believe has overstepped its authority and abused power in the nearly two years since Trump's inauguration.

They will have that opportunity, as congressional panels will be led by chairmen who have pledged to probe topics such as Trump's income taxes, his firing of attorney general Jeff Sessions, and the president's ties to Vladimir Putin.

Incoming chairpersons have signaled that Trump will face a barrage of probes that could bog down a White House already besieged by Special Counsel Robert Mueller's Russia collusion probe, draining energy from the administration's agenda and foiling Trump's message.

"It's on," Democrat Hakeem Jeffries, a new member of House leadership who is seen by some as a potential future House speaker, tweeted Wednesday.

"Tomorrow, we seize the majority. Then, we pass legislation to end reckless