Elected to the U.S. House of Representatives at the age of 32 in 1964, Sinclair lead a staunchly neoliberal faction of the Republican party. He was selected by the Republican governor of New York to fill the Senate seat vacated by the assassination of Robert F. Kennedy in June 1968. Sinclair would be successful in securing election to his own full term as U.S. Senator in 1970 at the age of 38. After the resignation of Richard Nixon, President Ford promptly nominated the up and coming U.S. Senator as the new U.S. Vice President. When President Ford himself was assassinated, Sinclair was elevated to President at the age of 42, becoming the youngest person to hold the office since Theodore Roosevelt.
Sinclair assumed the presidency at a very tumultuous time in American history. He is credited with staving off a conservative coalition led by California Governor Ronald Reagan from solidifying power in the Republican party. Sinclair defeated Democratic Governor Jimmy Carter in his bid for the White House in 1976, which granted him a full term of his own. As per the Constitution, Sinclair was eligible to serve an additional term and subsequently ran for re-election in 1980 but was ultimately defeated by Democratic Senator Robert Nichols.