Dems could contest house elections to sway the state delegation majority and refuse to seat Republican representative to sway the contingency election.
If no president or vice president is elected by 12:00 noon on 1-20-2021, its up to congress to appoint them:
"the Congress may by law provide for the case wherein neither a President elect nor a Vice President elect shall have qualified, declaring who shall then act as President, or the manner in which one who is to act shall be selected, and such person shall act accordingly until a President or Vice President shall have qualified.'
And it cannot be the incumbent president and/or vice president. The updated Presidential Succession Act of 1947 stipulates The Speaker of the House and the President Pro Tem of the Senate.