I think we are getting near to testing the question of whether or not a U.S. President, former U.S. President, or a candidate for U.S. President is above the law. I don’t think this question has ever really been answered/tested. Ford pardoned Nixon, so there never was an attempt at putting him on trial.
At the root of the question is whether our laws should be used for political gain. I think nobody would argue that laws should not be used for political gain, but doubt they never have been. On the other hand, the idea that anyone running for U.S. President is shielded from being put on trial does not seem right either as that means when one feels they are at risk they will simply declare their candidacy. I strongly suspect this is the reason why Trump declared he is running for President.
All of this reinforces how broken is the United States.