Pete Buttigieg’s campaign was hit with a complaint after a campaign finance watchdog group claimed his team improperly coordinated with a super PAC.

According to the complaint filed by the nonpartisan Campaign Legal Center, the former South Bend mayor’s campaign illegally accepted contributions of more than $639,000 from VoteVets, a super PAC backing Buttigieg’s campaign. The campaign was also accused of coordinating advertisements that ran in Nevada with the super PAC.

Super PACs, which are political entities that can raise unlimited funds from corporations and unions, are legally forbidden from directly coordinating with or donating to candidates. The complaint from the Campaign Legal Center claimed that a Buttigieg staff member, Michael Halle, tweeted a campaign strategy that was then carried out by VoteVets.

After Buttigieg claimed victory in Iowa, 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.”

On the same day that tweet was posted, Buttigieg’s campaign manager Chris Meagher welcomed VoteVet’s support of the former mayor, saying in a statement, “Pete is the only candidate who isn’t a millionaire or billionaire. And if the largest progressive veterans group wants to help spread the word about his service, we welcome it.”

VoteVets then poured $639,652 into television advertisements in Nevada that focused on the same talking points that were referenced in Halle’s tweet. Buttigieg’s campaign did not respond to the complaint, but the super PAC denied that the advertisements purchased by the group were coordinated with the campaign.

Joseph Sandler, a spokesman for VoteVets, said the PAC “has conducted all of its activities in full compliance with federal campaign finance laws and regulations.” He argued that Halle’s tweet “did not influence in any way VoteVets’s decision to run the advertisement or the timing, content, or targeting of the advertisement.”

Brendan Fischer, a director of federal regulatory work of the Campaign Legal Center, acknowledged that PACs and campaigns have tried to skirt coordination regulations by making public statements in the past. He claimed, however, that this was a step too far, telling the Washington Post, “This is different from what we’ve seen before, because the tweeted request is so obvious, including significant details about content, timing, location, and duration of the ads that the Buttigieg campaign was seeking.”

The Federal Elections Commission, the government agency responsible for reviewing campaign finance complaints, currently lacks enough members to review complaints. Even if it was functioning at full capacity, a complaint typically takes two years to be fully reviewed, meaning nothing will change before the Nevada caucuses on Saturday.

Buttigieg has been criticized by his fellow Democrats for accepting assistance from PACs and billionaire donors.