Though the principle of a self-pardon is untested in U.S. history, the Constitution does not explicitly forbid it.
In theory, if convicted of a federal crime, Trump could self-pardon. But would be powerless to do so against a state conviction.
As far as I know, any Espionage Act-related conviction (which is what the Mar-a-Lago search was about) would be federal law. However, Trump is in other kinds of legal jeopardy including violations of state election law in Georgia.
There is also the practical matter of convincing enough Americans to vote for him again, given the possibility of an indictment hanging over his head, the potential need to literally run a campaign from a jail cell, and *gestures vaguely at every other kind of Trump-related baggage*