The bitterly-fought Mississippi Republican Senate primary election overshadowed other primary contests across the country. It was seen as a multimillion-dollar referendum on the direction of the party as it tries to win control of the U.S. Senate in the November congressional elections.

Cochran, 78, has steered hundreds of billions of federal dollars to his impoverished state over a four-decade career in Congress, and courthouses and research centers throughout the state bear his name.

McDaniel argued that Cochran's nuts-and-bolts approach is out of step with voters in his deeply conservative state and promised to take a more confrontational approach to President Barack Obama and his Democratic allies in Washington.