SALEM — Gay rights backers kicked off a voter education campaign Monday aimed at eventually overturning Oregon’s ban on same-sex marriage.

Evan Wolfson of the national gay rights group Freedom to Marry said Monday he thinks “hearts and minds are changing” and that Oregon voters will at some point be willing to reverse their 2004 vote banning same-sex unions.

With states such as Massachusetts and Iowa now allowing gay and lesbian couples to marry, he said, people around the country “are realizing there is no good reason to exclude them from marriage.”

“They are seeing with their own eyes families helped and no one hurt,” said Wolfson, who traveled from New York to address rallies in Portland and Eugene.

The announcement of the Oregon campaign comes as voters in neighboring Washington state are deciding today whether to uphold that state’s domestic partnership law.

In 2004, Oregon voters passed a constitutional amendment defining marriage as being between a man and a woman.

The state’s largest gay rights organization, Basic Rights Oregon, thinks next year’s election would likely be too soon to take the issue back to Oregon voters.

Basic Rights officials said Monday they want to launch a statewide “conversation” with voters on the issue well in advance of placing something on the ballot, in 2012 .

“The heat of a campaign is no time to have a calm, heartfelt conversation about why civil marriage is so important” to gays and lesbians, said group’s executive director, Jeana Frazzini.

Gay rights advocates have been encouraged by the legalization of same-sex marriage in six states: Massachusetts, Iowa, Maine, Vermont, Connecticut and New Hampshire. They believe Oregon voters eventually will be ready to move in that direction.

The only way for that to happen in Oregon, though, would be to persuade voters to reverse themselves by repealing the state’s existing constitutional amendment banning gay marriage.

Tim Nashif, a conservative political consultant who led the 2004 campaign to pass Oregon’s gay marriage ban, said he’s seen nothing to indicate that the state’s voters have had a change of heart on the subject.

In the states where same-sex marriage has been legalized, he said, it’s been the courts or the legislature that have enacted those laws, not the voters.

“In California, one of the most socially liberal states, voters last year overturned a court ruling” legalizing same-sex unions, Nashif said.

He also said the same coalition of groups that worked to put Oregon’s ban on the 2004 ballot will make a major effort to defeat any effort to repeal it.

Oregon became one of the first places to allow gay marriage in 2004 when Multnomah County moved to legalize it. That lasted about six weeks until a judge ruled that there was no right to gay marriage under state law, thus invalidating 3,000 marriage licenses issued to gay and lesbian couples. Then voters approved the statewide constitutional amendment.,

Since then, the 2007 Legislature approved a domestic partners law giving same-sex couples some, but not all, of the rights and responsibilities afforded to married couples.