AUSTIN, Texas — A 91-year-old Texas congressman who first won his seat when Jimmy Carter was president faced the toughest test of his political career Tuesday from a Republican primary challenger barely half his age.

Ralph Hall, who first ran for political office in 1950 and is the oldest-ever member of the U.S. House, has promised that should he win an 18th term, it’ll be his last. But his opponent, John Ratcliffe, 48, was seeking to oust him in a primary runoff — claiming he’s the stronger conservative.