The conservative nonprofit advocacy group American Action Network raised more than $26 million for its efforts to support the agenda of the House GOP leadership in the fiscal year ending in June 2015, a record for the organization, according to new tax filings set to be submitted this week.

The robust fundraising shows how the nonprofit and its sister super PAC Congressional Leadership Fund have cemented their roles as the dominant outside allies of the Republican House leaders. The groups are currently in the strongest financial positions in their history, said Mike Shields, who is president of both organizations.

“You can see the group has ensconced itself as the House group,” said Shields, adding: “People know the brand. Some of the donors have been burned by other groups out there who promised certain things or weren’t as transparent, and this is an organization that has a really strong reputation in the donor community.”

Founded by veteran GOP fundraiser Fred Malek and former senator Norm Coleman, American Action Network and Congressional Leadership Fund serve as key allies of House Speaker Paul D. Ryan (R-Wis.). In the last year, American Action Network spent nearly $7 million on issue ads, including $3 million urging lawmakers to support Ryan’s fiscal policies.

A large share of American Action Network’s funding between July 2014 and June 2015 came from a single donor, who gave $15 million, tax documents show. Because the group is set up under section 501(c)(4) of the tax code, it is not required to disclose the names of its contributors.

“We benefit from having some investors who can give significant amounts to achieve these goals,” Shields said. “As the organization matures, that fundraising base will diversify.”

American Action Network plowed most of its money in the 2014-15 fiscal year — nearly $15 million — into a slew of campaigns promoting the House leadership’s agenda in the spring of 2015. The group spent $2.3 million supporting the House GOP balanced budget plan and $1 million calling on Congress to pass the Trade Promotion Authority. Another $1 million went into an effort to recruit and organize conservative grassroots activists.

“I feel really proud that in the spring of 2015 we were able to help the House leadership in getting TPA passed and other big-ticket items,” Shields said.

The group put about $10 million into political ads for Republican House candidates in 11 races, 40 percent of its spending. Nonprofit advocacy groups are permitted to make such direct political expenditures as long as they do not spend the majority of their money on such activities.

American Action Network doled out another $4.8 million in grants to other conservative groups, including $2.5 million to the National Rifle Association.