Republican senate candidate Steve Lonegan and wife Lorraine Rossi Lonegan, wave during his concession speech in Bridgewater, N.J., Wednesday, Oct. 16, 2013, after Democrat Cory Booker was declared winner. Lonegan and Booker were vying to fill the Senate seat left vacant after the death of Frank Lautenberg. (AP Photo/Mel Evans)

An already heated Republican primary in a South Jersey congressional district became even more acrimonious this week.

Insurance executive and former Randolph Mayor Tom MacArthur is suing his opponent, the conservative former Bogota Mayor Steve Lonegan, for defamation in response to statements Lonegan's campaign made alleging that MacArthur was accused of insurance fraud.

The two candidates are running in the June 3 GOP primary in the state's 3rd District to succeed Rep. Jon Runyan (R-N.J.), who is retiring.

MacArthur, who worked in the insurance industry for 30 years and was chairman and CEO of an insurance claims service firm, said that Lonegan’s campaign was being defamatory in highlighting cases in which the insurance firm MacArthur founded, York Risk Services Group, was sued by claimants arguing they had been underpaid.

MacArthur names Lonegan, as well as six of his campaign staff, in the defamation suit. The MacArthur campaign had sent cease-and-desist letters to Lonegan's campaign before taking legal action.

Lonegan held a press conference Tuesday where he called MacArthur's legal actions "bullying," according to The Philadelphia Inquirer.

“It's this kind of bullying and strong-arming of people that's downright despicable and has no place in this race,” a Lonegan press release read.

MacArthur's campaign responded by turning the attention back to the conduct of Lonegan's campaign.

"Steve Lonegan should look in the mirror. This is about his campaign and how they’re conducting themselves,” MacArthur spokesman Chris Russell said, according to the paper. “Steve Lonegan’s putting his own people at risk by running a campaign of lies and dishonesty.”

Runyan endorsed MacArthur as his successor last week, saying that a Lonegan victory could cost Republicans control of the district. Lonegan has high name recognition due to his unsuccessful race against Cory Booker in last year's special election to succeed Sen. Frank Lautenberg (D-N.J.), who died in office. He also served as director of the state's chapter of Americans for Prosperity, the Koch Brothers-backed conservative political advocacy nonprofit.