BOISE, Idaho — A proposal to write a ban on same-sex marriage into the Idaho Constitution was defeated today for the second consecutive year. A statutory prohibition remains in force.

The constitutional measure had majority support in the state Senate in a 21-14 vote. But that fell short of the two-thirds majority needed to send the constitutional amendment to a vote of the people. Eight Republican senators and six Democrats voted against.

The amendment would have invalidated any type of marriage or civil union except those between one man and one woman.

The bill's sponsor, Sen. Curt McKenzie, R-Nampa, said he would not try to pass an amended version of the bill this year. But the narrow margin of defeat means the bill will probably be considered at least once again next year.

The issue has been at the forefront of legislative issues since the session began Jan. 10, dividing friends, colleagues and even the Republican Party leadership.

Proponents have argued they are trying to protect traditional marriage from liberal, activist judges who want to expand the definition of marriage.

Opponents say the state should not discriminate against an entire class of people based on their sexual preference. They also argued the constitutional amendment was unnecessary and mean-spirited because gay marriage is already prohibited by law.