Chris McDaniel's campaign began its investigation into alleged voter "irregularities" Thursday morning in Hinds, the majority black county that Sen. Thad Cochran won Tuesday by 11,000 votes. 

WLBT reported Thursday that McDaniel campaign officials and supporters are going through voter books for individuals who voted in the June 3 Democratic primary. Mississippi has open primaries, so as long as a person didn't vote in the Democratic primary they were allowed to vote in Tuesday's runoff. Poll workers used the books from the Democratic primaries to prevent crossover votes, and according to The New York Times, turned away several ineligible voters. McDaniel's camp is still double checking.

Starting the search in Hinds County was no surprise. As we explained yesterday, Hinds is 69.8 percent black and voter turnout increased by nearly 50 percent between June 3 and Tuesday. That gave Cochran an additional 7,000 votes out of the 38,000 votes he gained in the primary, more than any other county. Overall, the surge in voting in majority black districts likely led to Cochran's win — FiveThirtyEight estimates that the senator would have lost by about 8 percent otherwise.

During his defiant post-election speech, McDaniel promised to "make absolutely certain the Republican primary was won by Republican voters." And while some of his supporters doubted his commitment to a possible legal challenge, he said Wednesday that his campaign will investigate. “In the coming days, our team will look into the irregularities to determine whether a challenge is warranted,” McDaniel said in a statement Wednesday night. “After we’ve examined the data, we will make a decision about whether and how to" proceed.