A Republican super PAC advocating for gay rights has spent over $500,000 on Illinois’ 11th congressional district race.

American Unity, a super PAC backed by New York hedge fund manager Paul Singer, has spent $517,849.57 on television ads attacking Democratic candidate Bill Foster, according to filings with the Federal Election Commission.

Foster, who served one term in the U.S. House of Representatives representing Illinois 14th congressional district, is facing off against 7-term incumbent Rep. Judy Biggert, a Republican currently serving the 13th district.

The new 11th district includes western suburbs like Naperville, Aurora and Joliet and is more Democratic than Biggert’s old 13th district. According to a recent poll released by the Foster campaign, the race is close. The poll, by Global Strategy Group, surveyed 401 likely voters in the district and shows Biggert with 43 percent and Foster with 42 percent.

American Unity would not return repeated messages for comment, but its website states it specifically backs Republicans who support gay rights.

The television ad running against Foster does not mention anything about the issue, but Foster calls both the ad and the group dishonest.

“You know it is actually a little bit strange to see this group presenting themselves as a Republican group supporting gay marriage since I’m a strong supporter of marriage equality and Congresswoman Biggert is not,” Foster said.

Gill Stevens, communications director for Biggert’s campaign, did not answer directly about Biggert’s stance on gay marriage in Illinois. Stevens did issue this statement via email:

“Consistent with her pro-LGBT record on other issues, Rep. Biggert has taken a very open view towards civil unions and legal rights among same-sex couples, and she thinks each state should be free to pursue its own course with respect to marriage.”

Stevens also declined to comment on American Unity’s support.

Both Biggert and Foster have voted to ban employment discrimination based on sexual orientation as well as stricter sentencing for anti-gay crimes.

Over $1.5 million of outside money has poured into the race, with just under $40,000 going to support Foster. That is according to the Sunlight Foundation, a campaign watchdog group. American Unity and another group, NEA Fund for Children and Public Education, together are spending over $1 million in the race backing Biggert.