Businessman Mike McFadden won the Republican nomination for U.S. Senate in Minnesota on Tuesday, advancing to a November showdown against Sen. Al Franken (D).

The Associated Press has called the GOP primary for McFadden, who easily defeated a field that included four other Republicans. He entered the day as the front-runner, having won the backing of the state GOP in May.

Franken, who got past a token primary challenger, begins the general election as a favorite. He's a popular politician and one of the best fundraisers in the Senate.

But Senate Republicans believe that if the midterm election is a GOP wave, McFadden could upset the first-term senator and former "Saturday Night Live" star.

Republicans need to gain six seats to win the Senate majority. ​

Sean Sullivan has covered national politics for The Washington Post since 2012.