A super PAC backing Republican Sen. Susan Collins’ reelection bid is pumping another $2 million into attack ads against her likely opponent, Graham Platner.

Pine Tree Results released a new attack ad targeting the presumptive Democratic nominee this week, directing viewers to a new website highlighting the 41-year-old political newcomer’s controversial past internet comments and his tattoo that resembled a Nazi image.

The super PAC so far has spent $4 million attacking Platner since Gov. Janet Mills suspended her campaign last month, effectively handing him the nomination.

The spending by the group, formed solely to bolster Collins’ reelection campaign, shows that Republicans are planning to keep up their attacks between now and the general election.

As of Wednesday, Republican groups had booked nearly twice as much airtime leading up to Election Day, spending nearly $73 million to Democratic groups’ nearly $42 million, according to the ad tracking firm Ad Impact.

Platner’s campaign, which is leaning on a populist message of taking on billionaires, dismissed the ads as a sign of desperation. His campaign manager highlighted the candidate’s grassroots support, including his roster of more than 15,000 volunteers.

“The super PACs can bring it on,” campaign manager Ben Chin said in a written statement. “It’s clear that the GOP establishment and the billionaire donors filling their pockets are rightfully panicking, because their senator is on the verge of being defeated by a Marine and an oyster farmer.”

Donors to the pro-Collins super PAC include Blackstone CEO Stephen Schwarzman ($2 million); Lexington Fund, a dark money group tied to the conservative activist Leonard Leo, who owns a home on Mount Desert Island ($1 million); and New Balance chairman James Davis ($1 million.)

Platner has apologized for many of his past comments on Reddit. He said he turned to online trolling when he was isolated, depressed and struggling with undiagnosed post traumatic stress disorder after serving four deployments in Iraq and Afghanistan.

He said he didn’t know a skull-and-crossbones tattoo he got on his chest with fellow Marines while in Croatia in 2007 strongly resembled a Nazi Totenkopf until last fall. But his former political director disputed that claim, noting the candidate’s affinity for military history. He covered the tattoo last fall.

The new Pine Tree Results ad accuses Platner of making “hateful and bigoted” comments for 20 years.

That timeline appears to extend back to when Platner was a high school student and coauthored a newspaper column urging Americans to understand the cause of terrorism. That piece expressly condemned terrorist acts, but it also said “one man’s terrorist is another man’s freedom fighter,” a line highlighted by the super PAC.

The ad calls out Platner’s comments criticizing police, the time he questioned why Black people don’t tip and his repeated use of slurs for people with disabilities and gay men. Few, if any of the disclosures appear new; those comments have been in the public domain since last fall.

The 30-second spot refers viewers to a website that highlights a broader swath of Platner’s old online comments, which were deleted before he ran for Senate.

Efforts to focus on Platner’s past comments and his controversial tattoo have been unsuccessful so far. He’s been able to outrun the scandals by crisscrossing the state and holding dozens of well-attended town hall events.

An independent poll released Wednesday by Pan Atlantic Research had Platner up seven points against Collins. But the survey also found that Platner’s net favorability has dropped nine points since March, which could indicate that the Republican attacks are having some effect.

Mills tried to argue that nominating Platner would be too risky, warning that Republicans would spend millions attacking Platner’s past comments. At one point, she predicted that the opposition would “make mincemeat” out of him.

Her campaign launched a late effort to highlight his past remarks blaming victims of rape and sexual assault. But she received swift backlash from her follow Democrats and pulled the ads.

Mills suspended her campaign in late April, citing a lack of money.

David Costello, a former government official from Brunswick, is also on the Democratic primary ballot. But his campaign has raised little money and it’s barely registered in the polls.