WASHINGTON (Reuters) - The U.S. Congress returns on Tuesday for a post-election “lame-duck” session, facing a funding deadline to prevent a partial government shutdown, as well as demands for protections for Special Counsel Robert Mueller and money for a proposed U.S.-Mexico border wall.

FILE PHOTO: Special Counsel Robert Mueller departs after briefing the U.S. House Intelligence Committee on his investigation of potential collusion between Russia and the Trump campaign on Capitol Hill in Washington, U.S., June 20, 2017. REUTERS/Aaron P. Bernstein -/File Photo

Those issues, plus leadership contests among both Democrats and Republicans, promise to dominate the brief session of Congress wedged in between last week’s congressional elections and the start of the 2019-2020 Congress in January.

In the elections, voters ended the Republicans’ majority control of the House of Representatives, giving it to Democrats, while leaving the Senate in Republican hands. New members will be sworn in the first week of January.

Until then, Republicans retain their dominance in both chambers, although Democrats already are ramping up challenges to their partisan rivals and Republican President Donald Trump.

“This election cycle really was about delivering a check to this administration, and it would be quite disappointing if we do not do that for the people,” Democratic Representative-elect Ilhan Omar of Minnesota told a news conference in Washington.

A House Democratic aide argued that the election results mean that Trump’s request for $25 billion to build a wall on the U.S.-Mexico border is “dead.”

The main legislative project for the lame-duck session will be a spending bill, said aides and lawmakers. Passage is needed to keep the Department of Homeland Security and some other agencies operating beyond Dec. 7, when the money runs out.

Some lawmakers hope to attach other measures to this “must-do” spending bill.

One example is emergency funds to help communities recover from a hurricane that hit mid-Atlantic states, wildfires raging in California and a typhoon that overwhelmed a U.S. territory in the Pacific Ocean.

Even with a smooth conclusion to this battle, the incoming Congress will immediately be faced with whether to avert $71 billion in mandatory military spending cuts along with $55 billion in non-defense program reductions next year.

MUELLER PROBE

For the current-year spending bill, Democrats and some Republicans want to attach legislation preventing Trump from impeding or ending the work of Mueller, who is leading an inquiry into Russian meddling in the 2016 U.S. presidential election and whether the Trump campaign colluded with Moscow to help Trump win.

Trump repeatedly has characterized the Mueller investigation as a “witch hunt” and has denied that he or his associates colluded with Russia. Moscow has said it did not interfere in the election.

Democrats and some Republicans worry Trump is maneuvering to fire or significantly restrain the special counsel.

Trump last week forced out Attorney General Jeff Sessions and replaced him with Matthew Whitaker as acting attorney general in charge of overseeing Mueller. Whitaker has described Mueller’s probe as being too wide-ranging.

The Justice Department said on Monday night that Whitaker would consult with ethics officials about any matters that could require him to recuse himself.

On another front, Trump has threatened to let some federal agency funding lapse unless Congress provides full funding for the border wall. He made construction of the wall a key campaign pledge.

Republicans and Democrats in the Senate and House must also choose new leaders, with Nancy Pelosi, the Democrats’ leader for the past 16 years, making a strong bid to become House speaker in a closed-door Nov. 28 party leadership election.

Pelosi made history from 2007 to 2011 as the first woman speaker, a position second in the line of emergency presidential succession after the vice president.