The nonpartisan watchdog group Campaign Legal Center (CLC) filed a complaint with the Federal Election Commission Tuesday that alleges the Buttigieg campaign improperly coordinated with the super PAC VoteVets on TV advertising in Nevada.

Background: On Feb. 5, Buttigieg campaign senior strategist Michael Halle tweeted, "Pete’s military experience and closing message from Iowa work everywhere especially in Nevada where it’s critical they see this on the air through the caucus."

A week later, VoteVets spent $639,652 to produce and run TV ads in Nevada that emphasized the same messaging from the campaign, per the complaint.

The CLC alleges that there is reason to believe the campaign therefore accepted more than $639,000 in "illegal and excessive in-kind contributions," a violation of federal rules that say candidates can't consult or suggest how independent groups spend their money.

"The tweet from Buttigieg’s agent is susceptible of no reasonable interpretation other than a request or suggestion for VoteVets — the only super PAC or other outside group supporting Buttigieg’s candidacy at that time," the complaint reads.

VoteVets’ lawyer denied wrongdoing in a statement to Axios, saying the super PAC made “independent expenditures to support the nomination of former Mayor Pete Buttigieg.”

The Buttigieg campaign did not yet respond to Axios' request for comment.

Read the complaint.