Senate Minority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellSessions: 'We should be like Canada' in how we take in immigrants NSA spying program overcomes key Senate hurdle Overnight Finance: Lawmakers see shutdown odds rising | Trump calls for looser rules for bank loans | Consumer bureau moves to revise payday lending rule | Trump warns China on trade deficit MORE's (R-Ky.) Tea Party challenger has lost a top staffer with just one month to go before the Kentucky primary, according to a local radio station.

Rachel Semmel, businessman Matt Bevin's top spokeswoman, is no longer with his campaign, WFPL reports. 

"Rachel has moved back to D.C. to pursue another career opportunity and is no longer with the campaign," Bevin spokeswoman Sarah Durand told WFPL. "The Bevin campaign is grateful for all she did for the team and wishes Rachel the best in her future endeavors."

Semmel left Rep. David SchweikertDavid SchweikertFive obstacles to Trump's infrastructure ambitions The Hill's Whip List: Where Republicans stand on tax-reform bill GOP Senate hopeful Kelli Ward leads challengers in internal poll MORE's (R-Ariz.) office last year to join Bevin's staff. 

WFPL also reported at least two field operatives have also recently left Bevin's campaign. 

The development is a setback for Bevin's campaign as he seeks to make up ground on McConnell, who has led by wide margins in the few public polls of the primary.