Lawmakers in Congress return to Washington Tuesday for a post-election session with substantial change just weeks away on Capitol Hill, as Democrats get ready to take charge of the U.S. House in January, signaling the start of more aggressive oversight of President Donald Trump and his administration.

"As we travel to Washington for this lame duck period, House Democrats are anything but lame ducks," said House Speaker Nancy Pelosi. "We are flying high and taking pride in the greatest Democratic victory in the House since 1974."

"We have great opportunity, and therefore great responsibility to get results for the American people," Pelosi added.

While Pelosi continued to celebrate Democratic gains - which now stand at 32 seats, and could grow further in ten undecided races - she is also trying to make sure she is the next Speaker of the House, as some Democratic newcomers have pledged to oppose her, like Joe Cunningham, who won an unexpected upset in South Carolina.

"I've said that from day one," Cunningham told MSNBC on Monday. "It's nothing against Nancy Pelosi personally, it's a matter of having new leadership."

Even as the new members were arriving in Washington for their freshman orientation meetings, Pelosi's office was busy on Monday churning out statements from senior Democrats, urging their new colleagues to back Pelosi for Speaker.

"Later this month, I will cast my vote for Nancy Pelosi to become our party’s nominee for Speaker of the House, and I urge you to do the same," wrote Rep. Elijah Cummings (D-MD), expected to be the next Chairman of the House Oversight and Government Reform Committee.

"The next Speaker of the House must be a shrewd, battle-tested negotiator," said Rep. Richard Neal (D-MA), in line to be the next Chairman of the powerful House Ways and Means Committee. "That's why I'm asking you to join me in supporting Nancy Pelosi for Speaker of the House."

While a number of new Democrats like Cunningham have said they don't want Pelosi to become Speaker again - no other Democrat has stepped forward to run against her.

There's still plenty of time for maneuvering among Democrats; they won't hold their leadership elections until the week after Thanksgiving.

While that Democratic leadership race will draw a lot of attention, the House and Senate do have legislative business to complete before they wrap up this session of Congress in December, as a series of spending bills must be finished, with a possible showdown over money for President Donald Trump's border wall.

Lawmakers will meet this week, and then take Thanksgiving week off, leaving little time after that for deal-making.

Other issues may also get resolved in coming weeks, as there were reports on Monday night from the New York Times that a bipartisan deal had been struck on criminal justice reform legislation, which has been pushed by President Trump's son-in-law Jared Kushner.