(CNN) -- The Rev. Billy Graham, the world's best-known evangelist, has endorsed a ballot initiative to constitutionally ban gay marriage in his home state of North Carolina, a rare move for a preacher who has typically avoided political fights.

North Carolinians will vote on the state's Marriage Amendment Act before North Carolina voters next Tuesday.

Voters will decide whether to amend the state constitution to say that "Marriage between one man and one woman is the only domestic legal union that shall be valid or recognized in this State."

North Carolina already bans same-sex marriages. The amendment would effectively ban civil unions and domestic partnerships, too.

Graham is taking out full-page ads in 14 North Carolina newspapers touting his support for the measure. His website he encourages churches to download a poster that bears his image and the message "Vote for Marriage May 8th."

"Watching the moral decline of our country causes me great concern," the 93-year-old pastor, who has prayed with every president since Dwight Eisenhower, said in a statement on the Billy Graham Evangelistic Association website. "I believe the home and marriage is the foundation of our society and must be protected."

The statement continued to say that Graham "never thought we would have to debate the definition of marriage."

Graham's newspaper ad will say: "The Bible is clear--God's definition of marriage is between a man and a woman. I want to urge my fellow North Carolinians to vote for the marriage amendment on Tuesday, May 8. God bless you as you vote."

The bill proposing the amendment says only a simple majority of votes is needed for the amendment to pass.

Supporters of the amendment hailed Graham's endorsement.

"Reverend Graham understands that we as North Carolinians have a duty to preserve God's first institution--marriage," said Tami Fitzgerald, Chairwoman of Vote FOR Marriage NC, a group supporting the measure, in a statement. "We cannot be silent as activists work to radically redefine marriage--an institution that has been fundamental to our civilization for thousands of years."

Opponents of the amendment lamented the move.

"While we were disappointed to see his endorsement it doesn't change much," said Paul Guequierre a spokesman for the Coalition to Protect North Carolina Families. The coalition, which includes pastors from across the theological spectrum, opposes the amendment. "We have respect for (Graham) but we will continue to work with our clergy on this."

"People across the country support LGBT equality," Guequierre said, adding his group was cautiously optimistic about the vote on Tuesday.

While Graham may be an internationally known figure, his influence in North Carolina may be even larger. Charlotte is home to the Billy Graham Parkway. When the Billy Graham Library opened in Charlotte in 2007, Bill Clinton, George H. W. Bush and Jimmy Carter came for the opening ceremony.

Graham's son Franklin Graham and daughter Anne Graham Lotz have both voiced support for the amendment and both have taken political stands in the past, in contrast to their father.

The-CNN-Wire/Atlanta/+1-404-827-WIRE(9473)

™ & © 2012 Cable News Network, Inc., a Time Warner Company. All rights reserved.