Supporters of same-sex marriage said Monday they’re aiming at a vote next year to reverse Oregon’s ban on gay marriage, which was approved in 2004.

The state’s leading gay-rights group, Basic Rights Oregon, said it has formed a campaign organization to get a constitutional amendment on the November 2014 ballot. The group will need to collect at least 116,000 valid signatures.

Voters in Oregon have become more inclined to support gay marriage since they approved the ban by a vote of nearly 57 percent to 43 percent, said Jeana Frazzini, Basic Rights Oregon’s executive director. Approval of gay marriage in other states and vocal public support from President Barack Obama have helped shift momentum with supporters of same-sex unions, Frazzini said.