WASHINGTON — The already odd GOP primary in Mississippi just kicked it up a notch.

Sheriff’s officials in Hinds County confirmed Thursday they were investigating a “bizarre” incident that left three supporters of tea-party front-runner Chris McDaniel temporarily locked inside the county courthouse where ballots had been counted on election night.

Sheriff’s spokesman Othor Cain said the department was trying to figure out how the three people gained access to the building after hours and ended up temporarily trapped inside around 2 a.m., long after election workers had put the ballots in a vault and gone home for the night.

Both campaigns seized on the incident as the latest down-and-dirty tactic in a primary that has upended Mississippi politics. Neither McDaniel nor longtime incumbent Sen. Thad Cochran cleared the 50 percent threshold Tuesday needed to avoid a runoff in three weeks.

“At some point, Republican voters in Mississippi need to say, ‘Is Chris McDaniel who we want on the national stage embarrassing us?’ ” asked Cochran spokesman Jordan Russell.

McDaniel supporters were arrested in connection with an incident last month when a blogger took a photo of Cochran’s ailing wife in her nursing home. McDaniel has distanced himself from the blogger.

Supporters of McDaniel, whose come-from-behind surge has put the 76-year-old six-term senator in a fight for his political life, have accused Cochran’s team of overreacting to both incidents in an attempt to halt momentum for their candidate.

“Sadly, the Cochran campaign wants to make this campaign about anything other than the issues,” said McDaniel spokesman Noel Fritsch. “Mississippians deserve better than this sort of distraction politics.”

The sheriff’s spokesman said the department was investigating but does not believe any ballots were tampered with during what Cain called a “very, very bizarre” incident. Only the hallways and restrooms were accessible, he said, and the ballots remained in a vault in a locked circuit-court office.

“We’ve got no reason to believe there was a breach in security in regard to the voting process,” Cain said.

The sheriff’s office identified the three who were trapped as Janis Lane, president of the Central Mississippi Tea Party; Scott Brewster and Rob Chambers.