Mississippi’s G.O.P. Senate Primary Headed to a Runoff

The hard-fought Mississippi Republican Senate primary is headed to a runoff between the six-term incumbent, Senator Thad Cochran, and his Tea Party-backed challenger, State Senator Chris McDaniel. Each received less than 50 percent of the vote in the achingly close first round of balloting on Tuesday.

With 100 percent of the vote counted, Mr. Cochran and Mr. McDaniel each had about 49 percent, with a third candidate pulling in less than 2 percent. Mr. McDaniel was leading by 1,386 votes out of the 310,000 cast.