Simeon II of Bulgaria is the most plausible candidate I can think of. He initially wanted to run for President in 2001, but he was controversially ruled ineligible due to supposedly not fullfiling the residency requirements by the Bulgarian Constitutional court. The decision was a narrow 7-5 ruling and three of the seven justices had been appointed by the current president, who was up for reelection (ironically he lost anyway and Sakskoburggotski, by then PM, doing his best to sabotage his candidacy certainly didn't help). So change the opinion of two justices without a conflict of interest in this matter and he would be able to run for President, where based in his personal popularity at the time he would be the favorite.