AUGUSTA — Two wealthy Democratic activists from New York have pledged $100,000 to Mainers United for Marriage, kicking off a four-week matching gift challenge in an effort to pass the gay-marriage proposal on November’s ballot.

Chris Hughes, a co-founder of Facebook, and his partner, Sean Eldridge, president of Hudson River Ventures, are pledging the money, said a statement released Monday by Mainers United for Marriage.

“Voters in Maine have a historic opportunity to win marriage at the ballot in November,” Eldridge said.

“We are encouraged by strong statewide support for the initiative and the top-notch campaign team that’s in place, and we hope that our support will motivate others to invest in the campaign. With numerous marriage equality cases heading to the Supreme Court, there is nothing more important than growing momentum and winning the freedom to marry in more states.”

Last week, President Obama’s announcement that he supports gay marriage boosted the hopes of its supporters.

But opponents pointed to a vote in North Carolina on a constitutional amendment to ban gay marriage, which passed with 61 percent support.

They said Mainers haven’t changed their minds on the issue since voters repealed a gay-marriage law passed by the Legislature in 2009

Bob Emrich, chairman of Protect Marriage Maine, which is opposing this year’s citizen initiative to legalize same-sex marriage, said he doesn’t think that Hughes or his past Facebook connection will have much impact on Maine voters, but his money could.

“Money raises money,” he said. “I suspect it will help us some as well. It will be a help to us to show they have big-money donors.”

Hughes, 28, left Facebook in 2007 with an estimated $700 million, and has helped raise money for Obama and other high-powered Democrats, according to The New York Times.

A feature story in the newspaper May 6 showed Hughes and Eldridge on their estate in New York and in their apartment in SoHo.

The story described the couple as “a significant force in political circles, becoming enthusiastic fundraisers for the progressive issues they support, which include gay civil rights.”

Hughes now is publisher and editor in chief of The New Republic.

In 2009, when voters rejected gay marriage in Maine, 53 percent to 47 percent, groups on both sides of the issue spent a total of $9.6 million to influence voters. Both sides say they expect a similar amount of spending on this campaign, with significant sums coming from out of state.

“This matching-gift challenge is critical to raising the early resources we need for our campaign,” said Matt McTighe, campaign manager for Mainers United for Marriage.

State House Writer Susan Cover can be contacted at 620-7015 or at: [email protected]