Bear in mind it wouldn’t be Trump vs Biden.
If enough House electors abstained from electing a president, it’d be down to the Senate who’d elect Pence over Harris (Ossoff and Warnock not being confirmed until after the vote)– and the winner of that would automatically become president without house delegations selecting anyone.
The question is whether enough Republicans in the House would abstain to get Pence into office.
This. If Cheney (or other R's in single member or closely split delegations) withheld her vote from Trump, the alternative isn't Biden. It's Pence. And that's a much closer call. Also, if you apply the uniform swing needed to flip Wisconsin to Trump, Perdue would win the regular GA senate seat outright in November, so a 51 vote GOP majority would be assured.
Factor in the likelihood that Trump's team would still be contesting PA aggressively into December to try to win outright, saying some crazy-sounding stuff in the process, and this gets even more interesting. How much of this would Cheney tolerate?
In your scenario where the House contingent vote deadlocks, the story doesn't end there. According to
Wikipedia:
To prevent deadlocks from keeping the nation leaderless, the Twelfth Amendment provided that if the House did not choose a president before March 4 (then the first day of a presidential term), the individual elected vice president would "act as President, as in the case of the death or other constitutional disability of the President". The Twelfth Amendment did not state for how long the vice president would act as president or if the House could still choose a president after March 4. Section 3 of the Twentieth Amendment, adopted in 1933, supersedes that provision of the Twelfth Amendment by changing the date upon which a new presidential term commences to January 20, clarifying that the vice president-elect would only "act as President" if the House has not chosen a president by January 20, and permitting Congress to statutorily provide "who shall then act as President, or the manner in which one who is to act shall be selected" if there is no president-elect or vice president-elect by January 20. It also clarifies that if there is no president-elect on January 20, whoever acts as president does so until a person "qualified" to occupy the presidency is elected to be president.
So Pence is just acting president indefinitely, waiting for the House to resolve the deadlock. At this point these Republican Congressmen/women would come under immense, overwhelming pressure from the Trumpists to vote for Trump. To be fair, they could justifiably say that these people have stolen the election from Trump. Given what we saw IRL it's plausible that these Republicans would be targeted for assassination by Trump and the 1/6 equivalent would have been an explicit kill mission.
