If they prove fraud occurred in those races, they could be over turned. The senate and house could change hands. All that is needed is one seat in the Senate and three in the house.
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The tiny problem with that proposition is simply, short of Democrats voluntarily ceding control of the voting system they worked do hard to capture, how do you suppose an election that might have such a result would be allowed to have that outcome?
It comes from the legislature. The senators and house members would have no choice.