An organization that describes itself as the nation’s largest lesbian, gay, bisexual and transgender civil rights group is donating $1 million to organizations in four states, including Maine, that have same-sex marriage measures on the November ballot.

The Human Rights Campaign, based in Washington, D.C., said the $1 million will be divided equally among same-sex marriage advocacy groups in Maine, Maryland, Minnesota and Washington. That means Mainers United for Marriage will receive $250,000.

Supporters of same-sex marriage said those funds will be used to pay campaign workers and for ads that are expected to start showing up on radio and television sometime after Labor Day.

“This is a tipping-point year in the fight for marriage equality that requires significant investment,” Human Rights Campaign President Chad Griffin said Sunday in a prepared statement. “We are committed to making sure this is the year that our opponents can no longer claim Americans will not support marriage equality at the ballot box.”

Last month, Maine Secretary of State Charlie Summers announced the final language for Maine’s Nov. 6 ballot question. The question will ask voters: “Do you want to allow the State of Maine to issue marriage licenses to same-sex couples?”

Spokesmen for both sides praised Summers’ decision, calling the language fair and easy to understand. They said the real battle will take place in the months leading up to the election as both sides try to win over voters to their cause.

Same-sex marriage has become a national issue. Voters in Maryland and Washington are being asked to affirm legislatively passed marriage equality laws. In Minnesota, voters will consider a constitutional amendment to ban gay and lesbian couples from marrying, according to the Human Rights Campaign.

“Bans on marriage for same-sex couples have sent the devastating message to young people that they cannot grow up to live their dreams and be full and equal citizens,” Griffin said. “This is the year we will change that.”

Bob Emrich, leader of the Protect Marriage Maine campaign, which opposes same-sex marriage, said that it’s “starting to look more and more like they will be flooding the state with money aimed at changing the definition of marriage.”

Emrich said he expects more out-of-state money to be invested by same-sex marriage proponents.

“It’s not because they care about the people in Maine,” he said. “It’s because they care about their movement. They desperately need a victory.”

However, Matt McTighe, campaign manager for Mainers United for Marriage, said, “It’s a huge investment at a time when we really need it to combat our opponents’ negative tactics.”

Opponents of same-sex marriage claim the Maine ballot question represents an infringement on religious freedoms, forcing clergy to marry same-sex couples even if it goes against their personal beliefs.

McTighe said that claim is false. The law will not penalize clergy for refusing to perform a same-sex marriage, supporters say.