A super PAC called Our Heritage Matters registered with the Federal Election Commission on Oct. 15.

Five days later, it began spending to boost third-party candidates and attack Republicans. By Oct. 29, the group had spent about $1.2 million across 10 House and Senate races, according to a CNBC analysis of FEC filings. What voters still cannot see is who supplied the money.

Because Our Heritage Matters formed after a key campaign finance reporting deadline on Oct. 15, its first regular report identifying its donors is not due until Dec. 3, a month after Election Day.

The group is an extreme example of a broader surge reshaping the midterm election: late-forming super PACs, including the latest-forming "pop-up PACs," pouring money into races before voters know where it came from.

Federal law requires super PACs and political committees to report large independent expenditures within 24 or 48 hours depending on how close to Election Day the spending occurs, showing how much they spent and which candidates they supported or opposed. Their donors, however, are disclosed less frequently through periodic campaign finance reports.

And in 2026, the practice of creating new, last-minute PACs has exploded. Both parties are using the tactic, with Republican-linked PACs spending about twice what those connected with Democrats have disbursed.

Twenty-two super PACs that registered with the FEC during the final 10 weeks before Election Day have each spent at least $1 million on congressional races, according to CNBC's analysis. Together, they had reported roughly $637 million in independent expenditures by Oct. 29 — about one-sixth of all independent spending reported in House and Senate races this election cycle.

The number of million-dollar late-forming super PACs has more than quadrupled since 2022, while their spending has grown nearly 35-fold.

At the same point in the 2022 midterms, just five comparable groups had spent about $18 million combined, according to CNBC's analysis. In 2018, three had spent about $12 million. The total has even eclipsed the past two presidential elections, when comparable late-forming super PACs spent less than $50 million combined on congressional races in both 2020 and 2024, according to CNBC's analysis.

"The reason for this is almost entirely to avoid disclosure, even if just temporarily," said Michael Kang, a Northwestern Pritzker School of Law professor who studies campaign finance. "Many times, if the donors were known, then it would undercut their cause." CNBC's analysis includes super PACs formed in the final 10 weeks before Election Day that spent at least $1 million on House or Senate races by Oct. 29. Spending includes regular FEC filings and 24- and 48-hour reports, with duplicates removed. One of the defining features of late-forming super PACs is speed.

Among the 22 groups in CNBC's analysis, 18 began spending within 30 days of launching, and almost all started spending before filing their first regular campaign finance report showing where their money came from.

“It’s happening more often, and they’re spending more money doing it because it works, and they’re getting away with it,” said Saurav Ghosh, director of federal campaign finance reform at the Campaign Legal Center. The group is a nonpartisan nonprofit founded by a former Republican FEC chairman.

Despite their late start, the groups accounted for more than 22% of independent expenditures in congressional races during CNBC's 2026 window, up from less than 2% at the same point in each of the previous two midterms.

Many are new only on paper. CNBC found financial or organizational ties between nine of the 22 groups and established political networks.

Lower Costs Now, for example, formed on Sept. 10 and disclosed an affiliation with the Future Forward PAC, the main outside group that backed former Vice President Kamala Harris' 2024 presidential campaign. Nineteen days later, Lower Costs Now began spending in Senate races.

But voters did not get a fuller picture of its financing until Oct. 15, when its first regular financial report showed that Senate Majority PAC, the main super PAC working to elect Senate Democrats, had given the group $23 million, according to FEC filings.

By Thursday, Lower Costs Now had reported about $75.5 million in independent expenditures across eight Senate contests, including Iowa, Texas, Kansas and Ohio, according to CNBC's analysis. Republicans have used the same playbook.

No Going Back PAC formed Sept. 1 and began spending three days later. Public reporting soon linked it to MAGA Inc., President Donald Trump's marquee super PAC. But its formal financial report did not arrive until Oct. 20 — more than six weeks after the spending began.

By then, No Going Back had already spent roughly $187.8 million, according to FEC filings, which revealed that MAGA Inc. had supplied the group with $200 million. By Thursday, the super PAC had spent roughly $242.2 million, according to FEC filings.

“They are a vehicle designed to emerge from nowhere and spend a bunch of money on an election” before voters can learn “who’s supplying that money and what their motivations might be,” Ghosh said. Many of the new groups are also narrowly targeted.

Fourteen of the 22 million-dollar super PACs identified by CNBC spent all of their money in a single congressional contest.

Take The Maine Standard. It formed Sept. 11 and began spending five days later. Since then, it has spent $8.2 million, all of it opposing Democrat Troy Jackson in Maine's Senate race, according to FEC filings.

The Cornhusker Majority followed almost the same pattern. It formed Sept. 10, began spending Sept. 16 and has spent about $7.1 million in Nebraska's Senate race, almost all of it opposing independent Dan Osborn, according to FEC filings. Osborn is running against Republican incumbent Sen. Pete Ricketts in a tight race.

The connection between the two groups did not appear in their regular financial reports until Oct. 15: Both were financed by Senate Leadership Fund, the GOP's main Senate super PAC.

On the Democratic side, Texas Forever launched Sept. 24 and began spending five days later, according to FEC filings. By Thursday, it had spent about $27.5 million to help Democratic Texas Senate nominee James Talarico, according to the FEC. Unlike some other pop-up groups, however, its initial FEC filing identified the Senate Majority PAC as an affiliate.

"A locally branded PAC doesn't necessarily hide where the money comes from, but it fragments the picture. Instead of seeing one national organization spending tens of millions of dollars across the country, voters see a series of different groups operating race by race," said Hilary Braseth, executive director of OpenSecrets, a nonpartisan nonprofit that tracks such spending.

But even identifying the national group behind a pop-up PAC can still leave another layer of the money trail hidden.

Texas PAC formed Aug. 28 and soon began spending to help Republican Ken Paxton in Texas' Senate race. The money flowed through the SLF, but Elon Musk's role was not public until Oct. 12, more than a month after the spending began.

On Oct. 15, FEC filings showed Musk had given the SLF $158 million in two contributions, with the group transferring matching amounts to Texas PAC the day after each donation.

By Oct. 29, Texas PAC had spent about $181.6 million in the race, according to FEC filings, making it one of the largest late-forming super PACs CNBC identified.

Together, Texas PAC and No Going Back accounted for roughly two-thirds of all spending by the 22 million-dollar groups. But the surge was much broader than those two giants: Even excluding them, the remaining groups spent nearly 12 times as much as comparable late-forming super PACs did at the same point in 2022.

"The growth is huge this year," Kang said. "Maybe you don’t want to be known this election, or want to hide away for a period while you might be unpopular, like AI is right now, but you kind of want to build a reputation for the players inside the system."