Win or lose, Trump absolutely should fight this out. Frankly, it doesn't really matter what voter fraud ends up proven in court; it matters what ends up "proven" in the court of public opinion - especially the opinions of the 70 million who voted for Trump.
So long as the Republicans hold the Senate (requires winning one of the two Georgia races to stop Harris from breaking ties), there is a hard limit on what a Biden administration can do. Especially when Republicans have refilled the judiciary under Trump.
The Republicans held onto state legislatures so that means Redistricting is going to favor them once again and SCOTUS set precedent last term that federal courts can't really intervene to redraw those maps.
The Dem's hold the House most likely but they will do so with razor thin margins which means that they get all the blame without having much leeway.
The RNC has seen the writing on the wall, the GOP is going to become a working class populist party and do so very quickly. The Lincoln Project Republicans? They aren't getting back in and their friends in Congress are going to get primaried in the next election.
Biden is going to face Senate investigations into his business dealings, if for no other reason than as payback for Russia-gate.
If you want the populist, nationalist, and working class party that Trump has built to last then get out, organize, and keep it. Build organizations, recruit like minded individuals, and prepare for next time.
When Jackson had an election stolen from him, he spent the next four years building a populist party and rode it into the Whitehouse. Don't let the Trump organizational apparatus collapse, maintain it, grow it, and recruit.
If a Republican in the House or Senate doesn't behave? Primary them.
And in four years? Run a candidate with Trump's fire but with a little less of the bombast and win. Give that person a House and Senate that is behind them and willing to give the government the enema that it needs. Run on an explicit campaign of investigating and purging the FBI, run from day one calling 2020 a stolen election and with an election integrity team that you have spent four years staffing, training, and preparing; have your own people with hidden cameras observing every single precinct in the dirty cities, have your people in every single counting location and camp outside them with all entrances under video surveillance the entire time.
If you want it, you can't rely on Trump, you need to d
Biden winning sucks, especially because it puts off the cleansing that the federal government so very much needs, but it isn't the end of the world. Biden with the House and Senate was always the real threat.