The 117th Congress will assemble on January 3, 2021. As the vote stands now, the Democrats will have at least 48 seats in the Senate. They successfully flipped Republican-held seats in Colorado and Arizona. And the Republicans will have at least 48 seats in the Senate. The Alaska and North Carolina races have not been called yet, but the Republicans will probably hold both seats. Therefore, I will presume that the Republicans will have at least 50 seats on the Senate.
The two Georgia seats are headed for runoff elections on January 5. One of them, Senator Perdue, will lose his position on January 3 when the new Congress meets. At that point, I believe the Governor can fill the Senate vacancy by appointment. (If I’m wrong about this point, please email me). Presumably, the Georgia Governor, a Republican, will select Perdue immediately upon their positions becoming vacant. The other Senator, Loeffler is already serving an unexpired term, and her appointment would continue until her successor is qualified. As a result both Perdue and Loeffler would then hold those seats until the results of the January 5 election are certified. It might only be for a few days.
If both Perdue and Loeffler prevail, the Republicans would then have a 52-48 majority. If one prevails, the Republicans would have a 51-49 majority. If both lose, the Senate would be split 50-50. When the Senate is split, the majority is determined by the vote of the Vice President, as President of the Senate. The Senate has only been evenly divided three times: 1881, 1953, and 2000. The most recent tie didn’t last long. In May 2001, Senator Jim Jeffords switched from the Republican party to the Democrat party, giving the Democrats control over the Senate.
Vice President Pence remains the President of the Senate until January 20. Therefore, with a 50-50 majority, the Republicans would still keep control of the chamber. With a 50-50 tie, during the period from January 3 through January 20, Senator McConnell will remain the majority leader. (Here, I will presume that the current votes hold, and Biden is elected). But on January 20, Vice President Harris would break the tie the other way for the Democrats. Senator Schumer would become the majority leader. And Senator Feinstein, or more likely someone else, would take the gavel for the Senate Judiciary Committee. The Committee could schedule votes on all of Biden’s nominees, and they would pass through on a party line vote. At that point, a floor vote would be held, and the nominee would be confirmed on a near-party line vote.
If the Republicans hold the Senate with a 51-49 or 52-48 vote, the Republicans would maintain control of the Senate Judiciary Committee. At that point, the Chairman of the Senate Judiciary Committee becomes, very, very powerful. He would have the power to decide which nominees receive a hearing and a vote. The chairman could effectively hold up nominations to the executive branch, as well as to the judiciary. Moreover, even if a hearing and vote is held, the Republicans could simply vote down Biden’s nominees. Imagine that the committee votes down Biden’s nominee for the Supreme Court. It is unclear that Leader McConnell would give a nominee a floor vote if he is voted down in committee. The more likely response is “nominate someone else.” I can even see a scenario where cabinet nominee are voted down. We may be stuck with Acting Attorney General Jeff Rosen for some time. (Remember Sally Yates?)
These thoughts are somewhat tentative. Please email me if I got anything wrong.
Update #2: Senator Perdue’s seat would become vacant, but Senator Loeffler’s will not.