Gay marriage opponent Bob Vander Plaats is preparing a campaign to oust Iowa Senate Majority Leader Michael Gronstal, the AP reported.

Vander Plaats, who helms the Christian conservative group The Family Leader, believes Gronstal has single-handedly blocked attempts to refer a gay marriage ban to Iowa voters. The constitutional amendment was overwhelmingly approved in the Republican-controlled House and is supported by GOP Governor Terry Branstad.

Over the weekend, Gronstal reiterated his pledge to block the measure from reaching the Senate floor.

“I'm not going to put discrimination into the state's constitution,” the Council Bluffs Democrat told the AP.

The issue has consumed Vander Plaats, who, after failing to secure the gubernatorial GOP nomination, spearheaded a campaign to remove three of the seven Iowa Supreme Court justices whose 2009 unanimous decision legalized gay marriage in the state.

He now says he'll work to unseat Gronstal.

“I think my political assessment of his decision is it will lead to his defeat in 2012,” said Vander Plaats. “Obviously he'll be a top target of ours.”

Democrats hold a narrow 2 seat majority in the Senate. Securing a Republican majority in the Senate would also alter its leadership.

Before voters can decide on a constitutional amendment, the measure would need to be approved by lawmakers elected in consecutive elections. That is, if approved in 2013, the earliest the question would appear on the ballot would be 2016.