The National Organization for Marriage (NOM) has donated $250,000 to the campaign that opposes Maine's referendum seeking to legalize gay marriage.

NOM on Thursday transferred the money to the Protect Marriage Maine political action committee, the AP reported.

Marriage equality supporters are returning the issue to the ballot box after voters in 2009 narrowly repealed a marriage law approved by lawmakers with a “people's veto,” known as Question 1. If approved, Maine would become the first state to legalize such unions with a popular vote.

Frank Schubert, campaign manager for Protect Marriage, called the upcoming vote “critical.”

“It is a critical race for the survival of the institution of marriage in this country,” Schubert said. “It's a race that the entire nation is looking at and will have an impact far beyond the borders of Maine.”

Schubert, who led the campaign for passage of California's gay marriage ban, Proposition 8, is also managing campaigns in three states where the issue will appear on the ballot: Maryland, Washington and Minnesota.

(Related: Maine gay marriage referendum tightens.)