Theodore Roosevelt was 24 when he was elected to the New York State Legislature and became President at 42. John F. Kennedy was 43 when he was elected President. Ted Kennedy was 30 when he entered the Senate. Andrew Jackson joined the Senate at age 29, created the Democratic party and had a donkey as his personal totem. The party used the donkey symbol in honor of him. Joe Biden joined the Senate at age 29, thirty eight years ago.