Pelosi elected to 4th term as House speaker

The Senate floor is open and Vice President Mike Pence is presiding over the swearing in of the new Senate.

Senators are presenting themselves in pairs -- in alphabetical order and accompanied by the other senator who represents their state -- where a masked Pence is administering the oath to each pair. The first pair of senators sworn in, Sen. Cory Booker, D-N.J., and Shelly Moore-Capito, R-W.Va., each elbow bumped Pence after taking the oath. 

The chamber appears almost entirely full and members are applauding after each administered oath.

The Senate will welcome six new members: Cynthia Lummis, R-Wyo., Ben Ray Lujan, D-N.M., John Hickenlooper, D-Colo,, Roger Marshall, R-Kan., and Bill Hagerty, R-Tenn. Sen. Mark Kelly, D-Ariz., was sworn in late last year. 

Two Senate seats remain outstanding pending the Georgia runoff elections on Tuesday. Sen. Kelly Loeffler will maintain her seat because it was an appointment, but Sen. David Perdue's term expires as soon as the new members are sworn in.

-ABC News' Allison Pecorin

The 117th session of Congress will begin with both chambers meeting at noon, as required by the Constitution. 

New members of the House and Senate will be sworn in under unusual circumstances given the pandemic, with social distancing and fewer family members and supporters in attendance. 

Because control of the Senate hinges on the Georgia Senate runoffs, Republicans will begin the new Congress with control of the chamber and a 51-seat majority. The seat of Sen. David Perdue, R-Ga., will be vacant until a winner is formally certified in Tuesday's runoff election.

Sunday afternoon, the House will elect a speaker.

Nancy Pelosi is expected to win with the narrowest of margins, given Democrats’ historically slim majority, but the vote is expected to take longer than last year because of the coronavirus precautions that require lawmakers to enter the chamber in waves.

-ABC News' Mariam Khan and Benjamin Siegel

Echoing his boss, Vice President Mike Pence is apparently supportive of the GOP senators and representatives planning to object to the Electoral College's certification of results on Wednesday.

"Vice President Pence shares the concerns of millions of Americans about voter fraud and irregularities in the last election," Marc Short, Pence's chief of staff, said in a statement Saturday night. "The Vice President welcomes the efforts of members of the House and Senate to use the authority they have under the law to raise objections and bring forward evidence before the Congress and the American people on January 6th."

Sen. Josh Hawley, R-Mo., said earlier this week he would support objecting to a state's voting results, likely one of several battlegrounds, thereby giving the necessary senator and representative to force a vote over the legitimacy of that state's results. Several GOP representatives had previously said they supported the challenge, but Hawley was the first senator. Seven others, including Ted Cruz, said Saturday they also supported it.

But challenging the electors in any state is extremely unlikely to prevent Joe Biden's confirmation as the next president. For a new slate of electors to be admitted, the Senate and House have to vote in favor. With the House controlled by Democrats, that will not happen and the original electors will be used.

A spokesperson for Biden called the move a "stunt" on Saturday. Several Republicans, including Mitt Romney, Lisa Murkowski and Pat Toomey, have come out against the move by fellow senators.

Pence will preside over the session on Wednesday to certify the vote.

ABC News' Elizabeth Thomas contributed to this report.

President-elect Joe Biden and his team are not showing any concern about the breakaway group of GOP senators planning to object to the results of the Electoral College on Jan. 6.

"This stunt won't change the fact that President-elect Biden will be sworn in on January 20th, and these baseless claims have already been examined and dismissed by Trump's own Attorney General, dozens of courts, and election officials from both parties," Biden spokesperson Mike Gwin said in a statement.

The group of senators -- close allies of President Donald Trump such as Josh Hawley, Ted Cruz, James Lankford, Martha Blackburn and others -- said they will object to the slate of electors in "disputed states" unless a 10-day audit is conducted of those states' results. Yet, dozens of lawsuits about the election results have already been rejected by both conservative and liberal judges.

"Once completed, individual states would evaluate the Commission’s findings and could convene a special legislative session to certify a change in their vote, if needed," Cruz and 10 other senators and senators-elect wrote in a statement Saturday. Hawley made his intentions clear earlier this week.

That audit appears unlikely and a rejection of the slate of electors would require a majority vote in both the Senate and House. The House lies solidly in Democratic control.

ABC News' Molly Nagle contributed to this report.