After slamming the speaker of the Virginia House for taking big bucks from the national Realtors association, his Republican primary challenger is getting some help from a conservative group that doesn’t disclose its donors.

A Pittsburgh-based political action committee paid for mailers on behalf of Susan Stimpson in her quest to deny William J. Howell a 15th term representing a Fredericksburg-area district south of Washington.

In line with Stimpson’s campaign theme, mailers with the banner “Public Service Announcement: Fact-Checking Speaker Bill Howell’s tax hikes” claim he is responsible for billions of dollars in tax increases.

Howell spokesman Matt Moran said the mailers “make you question the authenticity of her criticisms on fundraising and transparency.”

“We’ve been committed to running a positive campaign that highlights the speaker’s work in the community and his proven, conservative record in the House,” he said. “That’s not going to change because of false, negative attacks from a shadowy out-of-state super PAC.”

Susan Stimpson is challenging Virginia House Speaker William J. Howell for the Republican nomination for delegate. (Courtesy of Susan Stimpson)

Stimpson’s campaign consultant, Tim Edson, defended the PAC donation to the former Stafford County supervisor, who lags far behind the longtime incumbent in fundraising.

“Bill Howell’s a duplicitous tax-and-spend politician, so it shouldn’t be a surprise that there’s an outside conservative organization that wants to help Susan get her message out and push back against the mountain of lobbyist and special interest mail that Bill Howell has used to muddy the water and confuse voters,” he said.

Earlier this month, the political arm of the National Association of Realtors disclosed an in-kind donation of $40,000 for online advertising to Howell.

Edson on Friday declined to disclose the value of mailers funded by the Pittsburgh-based Freedom and Opportunity PAC and authorized by Stimpson under state campaign finance rules.

Michael G. Wallen, treasurer of and chief operating officer of the group, declined to comment.

The conservative PAC is tied to a political consulting firm founded by Sen. Patrick J. Toomey’s (R-Pa.) former campaign manager, according to federal reports.

“It’s unfortunate that Bill Howell has such a reputation for bullying people and punishing his opponents that there’s donors in Virginia who feel they have to run their money through an outside super PAC,” Edson said.

In the heated primary, Stimpson has tried to tap into the voter angst that helped Rep. Dave Brat (R-Va.) oust former U.S. House Speaker Eric Cantor. The election is June 9.