If Nixon hadn't been pardoned after his resignation, he would have been charged in federal court with multiple counts of obstruction of justice and criminal conspiracy. The evidence against him was overwhelming; most notably the tapes that he fought so hard to to keep, were damning.

I believe that Nixon, who was no dummy, would have seen the writing on the wall and entered a plea of no contest for an agreement of two to three years imprisonment to be served on a military base.