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On paper, there are restrictions designed to keep political groups within the domain of the FEC. But in practice, nonprofits have quickly found ways to spend hundreds of millions of dollars, with nearly all of their total expenditures having the potential to affect people’s votes.

“The way the law reads, it cannot be the primary focal point, so we read that to mean it means less that half,” Mr. Phillips said of restrictions on overtly political ads.

But Mr. Carroll questioned how ostensibly charitable organizations could have entire missions predicated on politics.

“It makes you wonder where are they spending the other 51 percent?” he asked. “My other question is how closely is that monitored in real time. If the groups are abusing the regulation, would anyone find out in time? If they were fined after the election, I don’t think they’d even mind paying it.”

Mr. Phillips said much of the rest of his group’s expenditures go to “issue ads” — many of them political advertisements that, while indistinguishable from overtly candidate-centric ads to the average viewer, avoid key words such as “vote for.”