Can the Senate or the FBI/DOJ establish a RICO investigation.
Not a lawyer, but IF RICO charges are to be pursued, it would be the DOJ, not the Congress. So winner of the election is irrelevant. It is possible the Congress has some hearings about cleaning up elections nationwide, but ultimately how elections are conducted, within the law, is up to each of the states (and counties/cities).
For decades the DOJ, under the Civil Rights Act(s), oversaw elections in southern states because of histories of voter suppression. That is long past, and now it appears the corruption of elections comes from the other side and it’s probably time for DOJ to get involved again.