Citizens United, the party in a landmark decision in which the U.S. Supreme Court declared that a corporate or labor union can spend without limits in donating to independent political groups, is now spending $18,000 on phone messages to urge Iowans to give three Iowa Supreme Court justices the boot.

Citizens United Political Action Committee is targeting 250,000 potential Iowa voters through robo-calls using Fox News host and former Arkansas Gov. Mike Huckabee to urge citizens to vote against the retention of three Iowa justices for their part in a unanimous 2009 ruling overturning a ban on same-sex marriage.

The disclosure report filed Friday by Citizens United came a day before the Des Moines Register released the latest Iowa Poll results finding likely voters are still split, but 37 percent say they will vote against the retention of the justices while 34 percent will vote to retain all three. Forty-one percent said they would probably not vote on the issue.

Citizens United joins several conservative groups including the American Family Association, the National Organization for Marriage, the Family Research Council and Concerned Women of America, who collectively have already spent more than $711,000 in efforts to urge Iowans against retention.

Last week the groups embarked on a statewide bus tour in Iowa featuring Rep. Steve King, R-Iowa, Rep. Louie Gohmert, R-Texas, Republican National Committee member Kim Lehman and former Sen. Rick Santorum, R-Penn., as speakers, in addition to Bob Vander Plaats, head of Iowa For Freedom, and Chuck Hurley, president of the Iowa branch of the Family Research Council.

The three justices were part of an April 2009 unanimous decision to overturn Iowa’s 1998 Defense of Marriage Act, co-authored by King, which limited marriage to be between one man and one woman.

Huckabee, considered to be a potential 2012 presidential candidate and won the Iowa caucus in his 2008 bid, endorsed Bob Vander Plaats in 2010 who ran unsuccessfully for the Republican nomination for governor the third time in 2010.

Several groups have formed featuring prominent Republicans in Iowa who are speaking out in favor of retention, although they are not spending nearly as much money.

Script of the robo-call:

“Hi, this is Mike Huckabee, and I’m calling for Citizens United Political Victory Fund urging you to vote ‘no’ on retaining Chief Justice Marsha Ternus … Justices David Baker and Michael Streit this coming Tuesday. The last thing this country and especially Iowans need are activist judges who put their own self interests ahead of the common good. Most Iowans and really a majority of Americans agree that marriage is a sacred vow between one man and one woman. That’s why these Justices should not be retained -and why I am urging to vote no on their retention! Thanks for your time and God Bless!

If you would like to be removed from our calling list, please call 866-635-8661. Paid for by Citizens United Political Victory Fund.”