If Trump is indicted in D.C. he will be convicted, and there is nothing short of stating CWII that can stop it.
Then the Republicans will be in the position of nominating a convicted felon for POTUS or someone who is indicted in multiple jurisdictions with felonies.
The Founding Fathers did not foresee that the US capital would be taken over by haters of the Republic and Constitution. Anti-American judge and jury. If they convict (jury pool is 90% anti-Trump), SCOTUS is unlikely to overturn it. I suppose it’s possible that a rational citizen could be a juror, but a hung jury would mean a lifetime of persecution for the juror and family.