The President of San Martin was the head of state of the Republic of San Martin.
In the period leading to the Invasion of San Martin by the People's Republic of Haven in 1880 PD, the office was held by Hector Ramirez, who was killed by Havenite forces, allegedly while attempting to flee. (HH2) Several other Ramirez family members died at the hands of Haven as well.
During the First Havenite-Manticoran War, after the retaking of Trevor's Star, Commodore Jesus Ramirez returned from the Havenite prison planet Hades. He had long been thought dead in the naval engagements at the time of the invasion. His unexpected appearance -- from the grave as it were -- resulted in his being drafted into running for President. He was elected by a landslide -- all but one candidate withdrew when he (Hector's nephew) returned and was proposed for the office. (HH9)