It is very clear that a second Trump term would be disastrous, so I am not really helped by explanations of how this would be so. What I have been looking for, is a clear laying out of the ways that he could claim the Presidency in the face of an electoral defeat on November 5th.

If enough state election boards in states where Biden wins the vote , fail to certify and send electors to get Biden the needed 270 electoral college votes... The House selects the president, with each state getting one vote. (Which means essentially, the GOP's choice wins).