Incumbent Ron Sandack voted for the measure and now mailings to voters in the district are reminding them of that vote. The district covers many southwest suburban communities.
"That's a concern of mine that we're really pitting neighbor versus neighbor," Sandack said. As Sandack went door-to-door in his district, he said there have been a few times where he's had to explain why he was one of three Illinois House Republicans who voted in favor of legalizing same-sex marriage.
"I'm trying to expand our party. I'm trying to win hearts and minds by being inclusive. And I think some folks don't like that," he said.
Keith Matune, a Downers Grove School Board member, is challenging Sandack in the GOP primary and calls himself the "clear conservative" in an online video. The anti Sandack campaign literature focuses on Sandack's gay marriage vote. It also includes a photo of two men kissing and Sandack with same-sex marriage supporters like Chicago Mayor Rahm Emanuel.
"The mail has been ugly, it's been innuendo-ridden and it's really unfortunate," Sandack said.
Sandack and his supporters fought back with their own mailers and a YouTube video with information about Matune's three separate arrests in the early 1990s. Court records show Matune was arrested in 1991 on a fugitive warrant for writing a bad check; in 1992 for public indecency; and in 1994 for criminal trespass. Records show the fugitive charge was dismissed but provide no further information. Court records also show Matune plead guilty to the indecency charge and the prosecutors did not pursue the criminal trespass case after Matune paid a fine. Sandack said what is worse is that Matune did not disclose the arrests when he applied for his Illinois teaching certificate.
"That's a character flaw and that's beyond an indiscretion that occurred in your youthful days," Sandack said.
"I was named Illinois Teacher of the Year last year because I stand up for conservative principles," Matune said in a video.
Matune, a social studies teacher at Waubonsie Valley High School in Aurora, did not respond to a request for an interview.
Sandack said he's a fiscal conservative and that his changed view of same-sex marriage is aimed at broadening the party's support.
"You only win elections when you're liked. And you can't be liked if people think you don't like them," Sandack said.
Editor's note: In an earlier version of this story we misreported that anti-Sandack mailers were sent out by Matune's campaign. Those mailers were sent out by various independent groups not his campaign. Also, in our earlier report, we incorrectly linked Matune's arrest for public indecency to his arrest for trespassing in a building that is now female college housing. Those were two separate arrests and are in no way related.