PORTLAND — The newly named manager of a campaign seeking to legalize same-sex marriage in Maine said he expects the campaign to spend more than $5 million ahead of November’s election.

The Maine Freedom to Marry Coalition announced today it has created a political action committee called Mainers United for Marriage to spearhead the campaign in favor of a referendum asking voters if they favor legalizing gay marriage.

Matt McTighe, who was named campaign manager, expects supporters will have to raise at least $5 million. Gay marriage advocates spent about $5 million in 2009, when residents rejected a statewide gay marriage referendum, he said.

McTighe said the campaign will focus on talking to Mainers one-on-one, in person and by phone, to make the case that gay marriage is about giving “loving, committed couples” the right to marry, just like heterosexual couples.

As the campaign gets close to the election, he said he wouldn’t be surprised to see gay marriage opponents use scare tactics and attempt to mislead voters.

“We’ve seen opponents of marriage in every state rely on these types of arguments because they know it’s worked in other states,” he said. “By scaring people they have been able to get people to retreat into some preconceived notion they had before they thought about it further.”

An opposition group is also forming a political action committee, called Protect Marriage Maine, said Carroll Conley, executive director of the Christian Civic League of Maine. The PAC was formed by the Christian Civic League, the National Organization for Marriage and the Rev. Bob Emrich, a pastor from Plymouth and chairman of the league, Conley said.

Referendum opponents expect to be outspent 2-1, Conley said.

His PAC is committed to being respectful and civil, he said, but he won’t be surprised if referendum supporters accuse opponents of using scare tactics for pointing out what they see as the “negative consequences” of same-sex marriages.

“I think in any political endeavor, if someone’s going to promote a certain action and you believe there are potential consequences and you point out those negative consequences, then you’re a ‘fear-monger,'” he said.

McTighe, 32, has been public education director in Maine for Gay & Lesbian Advocates & Defenders the past two years. He previously worked for the Human Rights Campaign and MassEquality.

His campaign’s website, www.mainersunited.org, was launched today.

The Maine Freedom to Marry Coalition is made up of EqualityMaine, Gay & Lesbian Advocates & Defenders, the American Civil Liberties Union of Maine, Maine Women’s Lobby, Engage Maine and 16 other organizations.