Michigan GOP Rep. Kerry Bentivolio's campaign manager recently left his campaign, his spokesman told Post Politics, a fresh sign of potential turmoil for a congressman facing a well-heeled primary challenger.

David Wolkinson ​left the campaign within the last week, said Bentivolio spokesman Matt Chisholm. Chisholm said the campaign will soon make an announcement about a new campaign manager. He declined to comment on the specifics of Wolkinson's departure.

Wolkinson, who did not immediately respond to a voice mail, was hired by Bentivolio last fall. He was a top policy aide on Republican Gov. Rick Snyder's 2010 campaign.

Bentivolio is facing a primary challenge from David Trott, an attorney backed by the Michigan Chamber of Commerce who put $800,000 of his own money into his campaign through the end of March and had more than a $1 million in the bank. Bentivolio has struggled to raise money; he had only about $129,000 in his campaign account.

The congressman's unlikely path to Capitol Hill started in 2012 after then-Rep. Thad McCotter (R-Mich.) failed to qualify for the ballot, suddenly leaving Bentovolio, regarded as a minor opponent, with the inside track. He defeated a write-in GOP candidate and then a Democrat in the general election.

Bentivolio's 2012 campaign manager Robert Dindoffer​ sued the congressman earlier this year over money he said he is owed.

The primary is Aug. 5.