Who is the strongest Democrat MTG can beat?

[Gary JG]

Biden.

Unlikely, even improbable, but not impossible.

Perhaps if Biden completely physically collapsed (like just barely alive) about a week before Election Day.

I was thinking about both of the two Democratic candidates dying right before the EC votes because the Democratic electors would then be unable to coordinate and vote for the same ticket. Then the election is thrown to a Republican House, which elects MTG.

If Biden or whoever else is fronting the D ticket dies soon before election day (this must be early enough in the early voting stage or before to prevent the original D ticket from receiving too many early votes), all the Democratic electors will go to his successor. The election has to already be close for the death to repel enough voters from the new D ticket - which isn't possible unless Biden's presidency turns out to be a disaster and he is blamed for it (consider the fact that the country was in a disaster scenario on Nov 3, 2020, and Trump was very close to winning. Regardless of whether Trump worsened the pandemic, he was not blamed by many voters for it or its fallout).

To put the point in general terms, if the expected winner of a Presidential election unexpectedly dies before or during the electoral voting on the day when the Electoral College members are voting and the electors do not get the news before they have cast their votes; the new Congress might have a difficult task sorting out who won. Presumably if the deceased candidate was a Democrat and there were Democratic majorities in both houses of Congress, they could avoid a contingent election by ruling that the votes for the late candidate were to be counted. Congress is not bound to follow the precedent set by an earlier Congress, when it ruled that electoral votes for the late Horace Greeley were invalid as cast after he died.

Similar logic could be used to elect the late Vice Presidential candidate if both nominees had died unexpectedly in the same time frame. The Presidential succession law could then be used to make the Speaker of the House, Acting President.

A Republican majority of both houses would presumably be happy to go for contingent elections, in the expectation that they would accumulate 26 House delegations and/or 51 Senators.

A divided Congress would presumably not secure a majority in both houses to throw out the state certified electoral  votes, so that would produce the Democratic preferred result.