Washington ? The Republican with the loudest presidential buzz says he won’t back a constitutional ban on same-sex marriage, in spite of its importance to conservative GOP primary voters.

Arizona Sen. John McCain said Sunday the controversial proposal to amend the Constitution would step on states’ rights.

“The states regulate the conditions of marriage, and unless there’s some decisive overruling by the federal courts, then I will continue to believe that the states should decide,” McCain said on “Fox News Sunday.”

“We in Arizona should make our decisions about the status of marriage in our state just as the people in Massachusetts and other states should make their decisions,” he said.

Many pundits believe a push to ban same-sex marriage in Ohio in 2004 helped President Bush beat John Kerry by boosting turnout among religious conservatives in what turned out to be the decisive state.