US Senator Thad Cochran of Mississippi has narrowly defeated challenger Chris McDaniel in a high-profile run-off election that pitted the Republican Party establishment against the insurgent "tea party" movement.
The bitterly fought election on Tuesday had become a multimillion-dollar referendum on the direction of the Republican Party as it tries to win control of the US Senate in November.
With 98 per cent of the votes counted, Cochran reportedly led McDaniel by 50.7 per cent to 49.3 per cent.
Cochran, 78, has steered hundreds of billions of federal dollars to his impoverished state over a four-decade career in Congress. McDaniel argued that Cochran's nuts-and-bolts approach was out of step with voters in his deeply conservative state and promised to take a more confrontational approach to US President Barack Obama and his Democratic allies in Washington. Cochran is strongly favoured to defeat Democrat Travis Childers in the November 4 election.