Conservative talk show host Rush Limbaugh on Wednesday blamed U.S. Sen. Thad Cochran's (R-Mississippi) upset primary win on "black Uncle Toms voters."

"I wonder what the campaign slogan was in Mississippi the past couple days. Uncle Toms for Thad?" Limbaugh, no stranger to racial controversies, said on his radio show, according to a recording from the liberal group Media Matters for America.

Limbaugh was referencing Cochran's unique strategy of reaching out to African-American Democrats, many of whom were allowed to vote in the Republican primary runoff.

"Because I thought it was the worst thing you can do, as an African-American, to vote for a Republican — the absolute worst thing that you could do! But somehow they were made to believe that votin' for 'ole Thad ... would be fine and dandy. And why? Well, 'cause they were told that Thad's done a lot for black people in Mississippi. It must be the first time that they've been told that," Limbaugh continued.

Limbaugh then turned his fire on the GOP establishment, which backed the incumbent's efforts.

"Insider Republicans in the Senate bought ... 8% or 9% from the black Uncle Tom voters in Mississippi," he said.

The radio host did not immediately return a request for comment from Business Insider.

Listen to the Media Matters recording below.