BOISE, Idaho —  A proposal to ban same-sex marriages has been defeated for the second consecutive year in Idaho (search).

The measure was defeated 14-21 in the state Senate on Wednesday after conservative supporters couldn't muster the two-thirds majority needed to send the constitutional change to a vote of the people. Eight Republican senators joined with six Democrats to form a blockade of moderates.

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

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, and they also argue that the legislation is unnecessary and mean-spirited because gay marriage is already prohibited by law.

Last week, the Senate State Affairs committee approved the legislation 5-4 after more than three hours of emotional testimony from gays, conservative activists, civil rights groups and clergy on both sides of the issue.