House Republicans’ flagship super PAC is relying heavily on “dark money” funding from an allied nonprofit to bolster its reserves as it plans an aggressive push to reclaim the House.

The Congressional Leadership Fund has received nearly $20 million from American Action Network, a closely tied nonprofit that does not disclose its donors. That total — which includes some in-kind contributions for research work — makes up nearly one-third of the super PAC’s fundraising this cycle. The Congressional Leadership Fund brought in over $7 million from its allied dark money group in June alone, according to new Federal Election Commission filings.

The cash boost comes as the super PAC readies a flurry of ads to boost Republican House candidates over their Democratic counterparts. The Congressional Leadership Fund plans to go on the offensive, reserving $43 million in Fall ads mostly targeting Democratic freshmen. Democrats hold a substantial majority in the House after flipping 41 seats in the 2018 midterms.