U.S. Senate candidate Graham Platner’s national finance director said Friday he is resigning from the campaign, citing differences in “professional standards.”

The announcement from Ronald Holmes is the latest shake-up for Platner’s campaign following a string of controversies. His Maine political director resigned earlier this month, citing inflammatory posts Platner had made on social media several years ago, and his campaign manager announced earlier this week he would be leaving, citing family reasons.

“I joined this campaign because I believed in building something different — a campaign of fresh energy, integrity, and reform-minded thinking in a political system that often resists exactly those things,” Holmes said in a post on LinkedIn. “Somewhere along the way, I began to feel that my professional standards as a campaign professional no longer fully aligned with those of the campaign.”

Platner, a 41-year-old military veteran and oyster farmer, is seeking to challenge Republican Sen. Susan Collins for her seat in 2026, though he’ll have to make it through the Democratic primary featuring Gov. Janet Mills and others first.

Holmes did not respond Friday to social media and phone messages seeking an interview.

“Ron helped the campaign reach out to big dollar donors, and we appreciated his efforts,” a Platner campaign spokesperson said in a written statement. “But the reality is our campaign’s fundraising success has come largely from small dollar donors. Nearly 90% of what we’ve raised has come from small dollar donations and online donors, which has been and is continued to be run by our digital fundraising director.”

Platner quickly and unexpectedly emerged as a front-runner in the Democratic primary after launching his run in August. His campaign reported having raised more than $4 million earlier this month, and a series of town hall events across the state have been well-attended, with voters seemingly drawn to Platner’s image as that of an everyday, working-class Mainer and his message that the political system needs to be overhauled.

In recent weeks though, the campaign has had to confront a series of old social media comments on Reddit that made national headlines and prompted Platner’s Maine political director, Genevieve McDonald, a former state lawmaker, to resign. The campaign then was roiled by Platner’s revelation that he had a tattoo resembling a Nazi symbol called a Totenkopf, which he has since had covered up.

Earlier this week, Platner’s campaign manager, Kevin Brown, a former senior adviser to Sen. Elizabeth Warren’s presidential campaign, stepped away after less than a week on the job, saying it was because he found out his wife was going to be having a baby.

While some staff changes over the course of a campaign are normal, the turnover “at a relatively high level over a short period of time” on Platner’s campaign is unusual, said Mark Brewer, a professor and chair of the political science department at the University of Maine.

“I would see it as a sign of concern within the campaign, especially given all the other stuff we’ve seen over the last few weeks,” Brewer said. “For me, it’s a sign of some internal turmoil or chaos.”

Brewer said he expects many voters won’t care about the staffing changes, though they could be a deterrent for donors.

At a recent town hall, Platner told supporters that the recent disclosures coming to light were a reflection of the political “establishment” trying to defeat him, and several attendees said they were not dissuaded from backing Platner because of them.

“But do donors care? Yes, a huge amount,” Brewer said. “I assume a lot of donors are looking at this saying, ‘Maybe we should hold off.’ Or in the worst case scenario for Platner, they’re saying, ‘Maybe we should double down on support for Mills so we don’t miss our best chance of unseating Susan Collins.'”

Brewer said he’s been surprised by the resilience of Platner’s campaign following the recent controversies, though he noted that President Donald Trump has changed the standards in today’s politics for what candidates can say and do and get away with.

“It hasn’t finished him off yet, but I think the key word is yet,” he said. “If the hits keep coming, I think at some point it will become too much. What that point is though, I don’t know.”