Supporters say state Issue 1, placed on the ballot by a petition drive, is necessary to ensure Ohio is not required to recognize same-sex marriages performed in other states.

The amendment also will ensure judges will not look for back doors into marriage by calling it a domestic partnership or civil union, said Phil Burress, the Cincinnati-area leader of the campaign to pass the issue.

"If somehow a court says we will not call it marriage, you are going to be unionized, it's just marriage by another name," Burress said.

But opponents argue the amendment is too broad and too vague, particularly the second sentence, which forbids a legal status for unmarried individuals "that intends to approximate the design, qualities, significance or effect of marriage."

Opponents say the amendment could affect legal contracts, visitation rights or property rights of any unmarried couple. There's also concern that it could affect a private company's ability to offer partner benefits.

"It is an ambiguous invitation to litigation that will result in unintended consequences for senior citizens and for any two persons who share living accommodations," said Gov. Bob Taft.

Attorney General Jim Petro has argued the amendment is so broad it will "cost us jobs and impair economic growth."

The issue has split Ohio Republican leaders. Taft, Petro, and U.S. Sens. Mike DeWine and George Voinovich oppose the measure. Secretary of State Ken Blackwell, Auditor Betty Montgomery and Treasurer Joe Deters support it.

State Sen. Jay Hottinger, R-Newark, a supporter of the amendment, said concerns about impact on business and the state economy are "baseless bunk."

E-mail jsiegel@enquirer.com