On Wednesday, Democrats will pick up a Senate seat when former astronaut Mark Kelly is sworn in as a US senator for Arizona.
Kelly defeated Republican Sen.
Martha McSally last month.
Other senators-elect will have to wait until January to be sworn in for the new Congress.
CNN reports that Kelly is able to take the oath of office right away since he won a special election.
The swearing-in is slated to take place Wednesday afternoon.
Party control of the Senate still has yet to be determined and now hinges on two Georgia runoffs set for January.