My guess is once it was advertised, promoted to Republicans and Disaffected Democrats, it would pull a very strong majority from the Republican party and grab disaffected Dems. I honestly think the here and now is the only time it could happen. The pain is too raw and the betrayal too deep and we the people saw what the Dems AND Republican leaders did...
If a new Party is created it can take it’s time to build a base. It doesn’t have to jump into the fray unorganized It needs someone to organize, make plans, fund raise etc.
The new party could during it’s growth still identify certain candidates to support and if they were to win then they would be beholden to the new party.