Against Lonegan is Tom MacArthur, a former insurance executive with support from the mainstream - the Republican committees in Burlington and Ocean - and the national GOP, which this week will elevate him to "contender" status in its program for top new candidates.
MacArthur talks of reining in taxes and spending, and repealing and replacing President Obama's health law, but in measured tones.
"I am a conservative Republican and I have been for my whole life," MacArthur said.
Lonegan, in another typically bone-rattling campaign, calls MacArthur a liberal.
"We've had enough of big government and my opponent is a big-government guy," Lonegan said.
Both are former North Jersey mayors who moved to the district this year after Runyan, the former Eagles player, announced he would not seek reelection.
MacArthur's bio on his campaign website describes his past work as "a local Mayor" but doesn't name the town he served - Randolph, 70 miles north of Burlington County.
Lonegan's site touts his work in the Bergen County town of Bogota.
Their scrap is playing out in a wide-open contest: The incumbent is out, Republicans have dominated House races in the district, but Obama won it in 2008 and 2012.
Lonegan, 58, is by now known to many voters. He has been on the public scene for nearly 20 years, first as an outspoken mayor, later as an activist who fought taxes and borrowing, and he has run three statewide races: twice in Republican gubernatorial primaries, and last year as the party's nominee for U.S. Senate.
"Steve Lonegan is a true conservative," said Bill Haney, vice president of the West Jersey Tea Party, which endorsed him. So has the national Tea Party Express.
But in a largely liberal state, Lonegan has been rejected in five runs for higher office. Establishment Republicans have scorned him in South Jersey.
In February, Assemblywoman Dawn Marie Addiego blasted his "angry" style, "callous" positions, and rhetoric that "drives away the middle-of-the-road voters we appeal to and win here in Burlington County."
MacArthur's campaign repeated the words callous and angry as the race intensified last week.
MacArthur launched two television ads pointing to Lonegan's opposition to a $50.5 billion federal relief package after Hurricane Sandy and his criticism of military spending as "bloated."
Both issues could strike a chord in a district that is home to the Dix-McGuire-Lakehurst joint military base, and is still recovering from Sandy.
"How do you leave people high and dry?" MacArthur asked.
Lonegan on Friday said the aid bill was full of "pork-barrel spending" and the federal response "a failure."
He also drew attention to an article by a British tabloid, the Daily Mail, that reported three instances in which the insurance company MacArthur built and led was accused of shortchanging institutions and individuals hit by hurricane and fire.
Lonegan predicted that if MacArthur wins, Democrats will use the story to tar him the same way they did Mitt Romney and Bain Capital.
"That's going to be the whole Democratic campaign, and it's going to be an effective one," he said.
MacArthur's camp called the article a planted "hatchet job" and the Lonegan tactics "despicable."
The Daily Mail writer has a history of collaborating with a researcher who is now paid by Lonegan's campaign; they previously cowrote stories on a conservative website.
The insurance disputes in the article - two in Texas after Hurricane Ike, one in California after a fire devastated a mobile-home community - were settled without any admission of wrongdoing, but are sure to provide lasting campaign fodder.
MacArthur, 53, who goes by "TMac" on his website and Twitter, moved to Toms River this year after owning a Shore-area home for eight years.
"He's very conservative on all the issues, but he's practical," said Bill Layton, chairman of the Burlington County Republicans. "That's the difference between him and Steve Lonegan."
A nasty primary in 2008 led to the GOP's only loss in the district in recent memory.
But Layton downplayed the tea party's power in New Jersey and said MacArthur didn't have to worry about exhausting his war chest in the primary.
"He'll have the money," Layton said.
MacArthur sold his insurance firm, York Risk Services Group, in 2010 for close to $500 million, and lent $2 million to his campaign in the first quarter of the year. (His only other fund-raising came from a single $1,000 contribution.)
He had a 10-1 cash advantage as of March 31, and that was after spending nearly $169,000 on television and radio advertising and mailers in late March.
MacArthur also donated $25,300 to the Ocean County GOP in December, months before winning the group's endorsement. Lonegan gave the organization $600 in February.
Lonegan, too, is new to the district - he bought a house in Lavallette this year - but stresses that he won the district in his Senate race against Cory Booker last year.
"If you talk to people in the street, they don't know who MacArthur is," said Haney, of the West Jersey Tea Party. "Steve has a well-recognized name."
Democrats have a more low-key primary: Burlington County Freeholder Aimee Belgard is running against Ocean County attorney Howard Kleinhendler. The party's Washington operatives are watching the GOP fracas with glee - even if analysts still predict a strong year for Republicans.
"Not one, but two carpetbaggers have their sights set on imposing their out-of-touch agendas on South Jersey," said Marc Brumer, a spokesman for Democrats' national congressional campaign, hinting at another bruising round to come.