Cochran's legal team sought to have the challenge dismissed, claiming McDaniel waited too long to file a primary challenge contesting the results of the June 24 runoff. McDaniel's campaign filed the challenge Aug. 4.
[UPDATE 4:45 p.m. EDT]
A spokesman for the McDaniel said the campaign's legal team would assess the ruling over the weekend and decide whether to appeal to the state Supreme Court.
"While we were intent on seeing the challenge through, as provided for by law, we certainly disagreed on this point of law," Noel Fritsch said. "We're disappointed that the facts of this case right now will not be heard in a public forum. That's certainly what it's all about."
A news conference is planned for Tuesday.
[Original story continues below]
McDaniel, a tea party conservative, won the June 3 primary but failed to top 50 percent of the vote, automatically triggering the runoff. Cochran, a Republican who has served in the Senate since 1979, pulled off what amounted to an upset, turning out Democrats to win 50.8 percent to 49.2 percent.
McDaniel refused to concede, alleging voting irregularities that he claimed were in violation of a state law that essentially prohibits voting in a party runoff if they have voted in another party's primary.
He said Cochran got Democrats who had voted in their own primary -- and ostensibly planned to vote for a Democrat in November's general election -- to vote in the runoff. Cochran's team denied any wrongdoing.
Cochran will face Democratic Rep. Travis Childers in November.