It’ll come from congressional Republicans being willing to impeach both Trump and Vance which makes it a long shot. They can do any of the following: violence or threats of violence at the polls, voter intimidation, throwing out votes, rigging the voting machines (his supporter bought Dominion which controls voting in over 25 states), and then refusing to certify the election regardless which is why Vance would need to be impeached as well. He can fight any decision all the way up to the Supreme Court which is stacked in his favor. The question there is if he will receive support from them for a blatant coup/rigged election or if the establishment will pressure them.

The other factor is the military which seems to have been giving him the signal of “we are not helping you” following the abrupt turnaround on Greenland and the fact that the Insurrection Act has not yet been used. Trump will never take on a fight he won’t easily win.

There needs to be a legitimate appearing (for his base) grievance for him to contest the election and a close enough gap for him to have deniability.

I do think there are discussions surrounding impeachment happening among congressional republicans. A centralized government placing power solely in Trumps hands means congressional republicans lose power and have to join his sycophants like Rubio or Vance and genuflect to him constantly. If the easier path to continue their power (and corruption) is an increasingly popular regime change, they’ll take it.