Democrat Scott Colom has won election to the U.S. Senate in Mississippi, securing victory in what became the closest Senate race in the country and defeating incumbent Republican Sen. Cindy Hyde-Smith.

The Associated Press called the race, marking a historic shift for Mississippi, which had not elected a Democrat to the U.S. Senate in more than 40 years.

The outcome concludes a tightly contested campaign in the state, bringing an upset victory for Colom as he flips the seat previously held by Hyde-Smith.