The National Organization for Marriage (NOM) is targeting Democratic candidate Liz Mathis, who is running for the Iowa Senate seat being vacated by Democratic Senator Swati Dandekar.

The November 8 race could determine whether gay marriage is debated in the Senate.

The Democrat-controlled Senate, under the leadership of Majority Leader Michael Gronstal, has kept an effort to repeal the state's gay marriage law at bay. In February, the Republican-controlled House approved a measure that seeks to put a question on the ballot that would define marriage in the Iowa Constitution as a heterosexual union – and thereby reverse the 2009 Iowa Supreme Court ruling that brought gay marriage to the Midwest.

Gronstal has vowed to block the measure from reaching the Senate floor.

But Republican Governor Terry Branstad's appointment of Dandekar to the Iowa Utilities Board could result in Democrats losing their one-seat Senate majority. And by extension, stripping Gronstal of power. In previous sessions where the Senate was divided, leaders from both parties took turns on alternating weeks running the chamber.

In its mailer, NOM supports Republican Cindy Golding, whom the group claims opposes marriage equality.

“The future of Iowa families in the balance,” the mailer reads. In a bullet point, the mailer notes that Mathis “Thinks Iowans have no right to vote on [the] definition of marriage in Iowa.”

“This is a pivotal election contest in our battle to allowing [sic] the people of Iowa the opportunity to vote to restore marriage,” NOM President Brian Brown said in a statement.

Both candidates, however, have downplayed the issue.