Unite the Country PAC, which was launched in October by longtime advisers to the former vice president and allies of former President Barack Obama, has spent $2.3 million on TV ads in support of Biden in Iowa, according to recent disclosures .

Biden had disavowed the support of Super PACs early in his campaign, but walked that position back just before Unite the Country launched in October. The timing of the launch comes with an additional benefit: The PAC will be able to keep its donors under wraps until just three days before the February 3 Iowa caucus. Under Federal Election Commission rules, the Super PAC’s first disclosure is due on January 31. The schedule gives Biden more of a chance to escape scrutiny of who exactly is bundling for the PAC — a list likely to include more major industry players , far and away from the working-class voters for whom Biden has cast himself as a hero. Asked about the date the group was required to file its next disclosure, a spokesperson for the PAC said it followed the FEC’s reporting schedule. The Biden campaign did not respond to requests for comment.

In recent years, political campaigns have devoted more of their resources to digital advertising and email distribution, but they continue to spend big on TV ads. For candidates like Biden, whose campaign had been struggling with fundraising in the fall, Super PACs can play a key role in helping reach people on the airwaves.

Among other Democratic frontrunners, the Warren campaign has no Super PAC, while Sanders has the support of outside operations such as the National Nurses United, Democratic Socialists of America, and Our Revolution, though none will be doing TV ads or spending heavily.

The Super PAC affiliated with National Nurses United, which endorsed Sanders in November, spent $5 million to support his 2016 campaign, including a significant portion on ads. So far this cycle, it has not purchased any ads in favor of the candidate. As of its last FEC filing in July, NNU reported spending only $893, with $1,638 cash on hand. Its next filing is due on January 31. The PAC declined to comment for this story. The Democratic Socialists of America, which endorsed Sanders in March, has an independent expenditure to support him, and had spent roughly $28,000 as of its last filing in October. The group spent a little over $87,000 to support him in the 2016 election.

Buttigieg, meanwhile, is backed by the VoteVets PAC, which is the largest PAC supporting veterans running for office. When the group endorsed Buttigieg last month, it said it would spend money on social media and email distribution, and would also focus on opposition research. A spokesperson for VoteVets said the organization would not “comment on our ad strategy in early primary states,” and as of its most recent disclosure in December, it had not yet spent any money in support of Buttigieg. Early in his campaign, Buttigieg said he would reject corporate PAC money, but did not fully swear off support from Super PACs. Asked by the New York Times if he would request the VoteVets PAC to stop spending on his behalf, Buttigieg said he would not “get involved in that.”

The debate over campaign finance has featured heavily during the Democratic primary, including during a contentious dispute between Warren and Buttigieg at last month’s presidential debate.

Biden entered the race saying he would reject support from Super PACs, which can raise unlimited amounts of money to support candidates of their choice. His campaign reversed that position in October just before Bloomberg reported Unite the Country’s launch. Biden has also sworn off contributions from lobbyists and fossil fuel companies, but has continued to hold fundraisers with lobbyists and key figures in the financial and fossil fuel industries.

Last month, the PAC filed a list of independent expenditures to various contractors. That included a $624,000 Iowa ad buy from Old Town Media, a firm based in Alexandria, Virginia. The PAC spent an additional $36,400 on ad production with two firms: Assemble the Agency, based in New York, and Putnam Partners, based in Washington, D.C.

Buttigieg in May shut down his Hitting Home PAC, which he launched in June 2017 following an unsuccessful bid to become chair of the Democratic National Committee. The PAC was focused on supporting Democrats in the 2018 cycle. Despite his pledge not to accept corporate PAC or fossil fuel money, Buttigieg has continued to hold private fundraisers with corporate executives very much intertwined with the fossil fuel industry, including Blackstone.

Sanders, for his part, is also backed by Our Revolution, a 501(c)(4) nonprofit political organization he founded as an offshoot of his 2016 presidential campaign. While the group is not technically a Super PAC, it can raise unlimited sums as if it were one but does not have to disclose its donors. (The group does disclose the names of its donors, though it does not identify the size of their contributions.)

Sanders leads the fundraising field by far; his campaign announced last week that he’d surpassed 5 million donations from more than 1.2 million people, and that he raised $34.5 million in the fourth quarter. Buttigieg raised $24.7 million, Biden raised $22.7 million, and Warren raised $21.2 million.