".... Congress is required to assemble, determines by two-thirds vote of both Houses that the President is unable to discharge the powers and duties of his office, the Vice President shall continue to discharge the same as Acting President; otherwise, the President shall resume the powers and duties of his office."
In other words, even if they lose the Senate, Republicans have the power to leave Jill Biden as functioning President and negotiate her agenda under the threat of removing Joe from the White House.
Grab your popcorn fans, this political soap opera could get very interesting.