This would be a case of first impression.
The constitutional assumption is the President is there legitimately and what he does AFTER in office is outlined. The Constitution doesn’t contemplate a fraudulent election process. The Court would need to adhere to sound constitutional intent.
It seems to me that if there was enough of the right kind of evidence the Court could rule the election and its results null and void and take it from there.
To me, this is like a RICO (Racketeer Influenced and Corrupt Organizations Act) case.
The Constitution does contemplate a way to head off fraud in an election - but the time frame and process has passed. The process is the electoral college.
There is no Presidential election in the Constitution, fraudulent or otherwise.