Supporters of same-sex marriage say 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 Monday it would form a campaign organization to get a constitutional amendment on the November 2014 ballot.
Voters in Oregon approved the ban on gay marriage by a vote of nearly 57 percent to 43 percent.
But Basic Rights Oregon said in a statement that approval of gay marriage in other states and shifting public opinion has put momentum on its side.
A spokeswoman for the Oregon Family Council told The Oregonian the group has been preparing to oppose such a measure and said both sides would have a difficult fight.