After donating $10,400 to their son's campaign, Strouse's parents gave nearly $50,000 to eight other candidates between June and December, Federal Election Commission records show.
The parents of at least four of those candidates donated to Strouse's campaign for the Eighth Congressional District seat, usually in identical amounts and days before or after the Strouses' contributions. The parents had already given the maximum to their own children's campaigns.
Despite multiple requests, Strouse, his parents, and campaign have declined to discuss the donations - and did so again after Naughton spoke out Wednesday.
"This is nothing more than a desperate attempt by the Naughton campaign to distract voters from the hypocrisy of her connections to the fracking industry," Strouse spokesman Brendan McPhillips wrote in an e-mail. (Each candidate has accused the other of taking money from individuals tied to natural gas companies.) "Democrats who engage in desperate negative attacks against fellow Democrats are set to lose up and down the ballot on Tuesday."
Campaign finance experts contacted this week by The Inquirer were split on the propriety of the donations. Two said that if the parents or others made an explicit agreement to trade donations, that could amount to a bid to circumvent the limit on federal campaign contributions.
Two others said they believed the payments were legal even if there was such an agreement.
The only obvious link between the candidates or their parents is that each campaign has been prioritized as among the most critical House races for national Democrats.
Strouse, a former Army Ranger, is the Democratic Congressional Campaign Committee's handpicked candidate for the swing seat covering Bucks and part of Montgomery Counties.
The DCCC has declined to say if it had a role in introducing the donors or directing their contributions. Its only comment was a two-sentence statement Monday that said in part: "These races generate tremendous enthusiasm from our allies and candidates' own networks."
Naughton briefly mentioned the parental contributions during a debate last month. On Wednesday, she told reporters that Strouse should explain what he knew about the donations, if he approved of them, and if his campaign coordinated them.
"Was there a quid pro quo?" she asked. She also called on him to return the roughly $28,400 in parental contributions - less than 4 percent of Strouse's overall fund-raising - if they were part of a plan to get around donation limits.
"Frankly, if it's not illegal, it certainly seems like it should be," she said.
But her campaign later said she would not file a formal complaint to federal election officials.
Both Strouse and Naughton, a businesswoman, are first-time candidates. The winner of the primary will face the incumbent Republican, Mike Fitzpatrick, in the fall.
Strouse has been seen as the front-runner throughout the race - in part because of his party backing.
On Wednesday, Naughton trumpeted an endorsement from former Gov. Ed Rendell, who called her "the most qualified candidate" in the race and the one "with the best chance" to beat Fitzpatrick.
Strouse's campaign responded, saying it had the backing of 10 labor organizations and dozens of local officials.