In the bit of cable news I watched there was much gnashing of teeth over the Mar-a-Lago classified documents decision. Judge Cannon apparently takes Trump's claims of Executive Privilege seriously. While I am not overly concerned, it is a clear example of our two justice systems: one justice system for the rich and another justice system for the rest of us. Every shoplifter, burglar and armed robber caught red-handed with the goods would love to have his day in court delayed by a special master's itemization of the stolen goods mixed with the miscreant's personal possessions.
That said, I am unconvinced that it's a get out of jail free card for Trump.
For starters, the DOJ may seek an appeal(s) which may negate all or part of Judge Cannon's decision. Now if the case goes all the way to the Supreme Court, bear in mind that SCOTUS has already ruled against Trump's claim of Executive Privilege.
Secondly, Judge Cannon ruled that the DOJ can't investigate the documents under scrutiny. But the DOJ already went through all the documents. They know each and every classified document in question (Trump's personal papers are irrelevant) that the FBI collected in their August search. Also the DOJ knows what Trump voluntarily surrendered last June and earlier. So what evidence is there to investigate? The DOJ has more than enough evidence to build their legal case against Trump. Everything has been photographed. They've probably checked for fingerprints.
Finally, the special master at worst delays matters; it doesn't end matters. Dragging things out is bad news for the Republican candidates. Prolonged reports about Trump's legal matters doesn't help their case. The non-Trumpies, the rational Republicans and independents sense the inequities of the justice system and how Trump abuses the system. Violating the Espionage Act et cetera is not popular with most voters. Undoubtedly Trump will continue to talk about how he is a victim. That's not what Republican candidates want to talk about.