(Adds statements by McDaniel campaign in paragraph 3 and Cochran campaign in paragraph 8)
By Emily Le Coz
JACKSON, Miss., Oct 24 (Reuters) - The Mississippi Supreme Court on Friday rejected a Republican primary challenge by former U.S. Senate candidate Chris McDaniel, possibly ending his legal effort to overturn the June result that he alleged was stolen by incumbent U.S. Senator Thad Cochran.
In a split decision, justices affirmed a lower court ruling dismissing McDaniel's case, saying he filed it after the statutory deadline.
"While we disagree with the majority, since there was no deadline in the statute to file a challenge, we are glad the Supreme Court finally ruled so Mississippi conservatives can move forward into 2015," McDaniel's campaign attorney, Mitch Tyner, said in a statement.
Mississippi law allows a candidate 20 days after a statewide primary election to contest the results. McDaniel, a Tea Party-backed candidate who ran a fierce campaign, filed his challenge 41 days afterward.
McDaniel argued the deadline no longer mattered because the courts had already considered a 2004 election challenge filed 34 days after a primary, but the justices disagreed.
"We are not persuaded by his argument," Justice Leslie D. King wrote in the 30-page order. He was joined in his opinion by three other justices.
Two justices dissented, including Josiah Dennis Coleman, who called McDaniel's charges "too substantial and material" to be constrained by the deadline and said he would have reversed the lower court's decision.
"Today's ruling by Mississippi's highest court brings an end to the challenge of the primary runoff election and reconfirms the voters' choice of Thad Cochran as the Republican nominee for U.S. Senate," according to a statement by lawyers representing the Cochran campaign.
The decision comes four months after the June 24 primary runoff that McDaniel lost to Cochran by roughly 7,700 votes.
McDaniel refused to concede, claiming that Cochran encouraged voter fraud and that thousands of ballots had been improperly cast by Democrats, mostly African-Americans, or mishandled by county election officials.
His campaign appealed to the state's high court after a circuit court judge, determining his lawyers had taken too long to file an initial complaint with the state Republican Party, dismissed the claim last month.
Cochran's campaign had maintained that McDaniel's challenge was without merit and said that Cochran was focused on the Nov. 4 general election. (Reporting by Emily Le Coz; Editing by David Adams and Eric Beech)