The general principle -- for choosing a Pennsylvania state legislator or for choosing Presidential electors -- is that the office goes to the person who got the most votes. In Marks v. Stinson, the ruling was that the candidate who had initially been certified as the winner had not actually gotten the most votes. In the states Trump carried, resulting in the election of 306 electors who supported him, those electors actually did get the most votes, AFAIK. Marks v. Stinson would apply only if there were clear evidence to undercut that conclusion, such as proof that voting machines were hacked or, as in that case, that fraudulent absentee ballots were cast.