The nation's most vocal opponent of gay marriage is preparing to lead the fight in the District of Columbia as a new law that recognizes legal gay marriage takes effect Tuesday.

The National Organization for Marriage (NOM) has been vociferous in its opposition to gay marriage victories this spring in Maine, Vermont and New Hampshire.

In a Tuesday tweet, NOM said: “I've arrived in DC and am opening up our DC office. Keep us in your prayers.”

The District's marriage recognition law went into effect Tuesday after a 30-day review period by Congress, and lawmakers say they will introduce a gay marriage bill in the fall.

The Maggie Gallagher-led group is also attempting to influence the outcome of a gay marriage bill waiting for Senate approval to became law in New York.

The group is threatening to boot out Republican senators who vote in favor of the gay marriage bill. NOM announced last month it will use funds raised through its New York PAC to back primary challengers of GOP senators who do not support their anti-gay marriage position, and will reward Democrats who do.

In Maine, NOM has partnered with the Catholic Diocese of Portland to create the Stand for Marriage Maine coalition. The new group is organizing a “people's veto” to repeal gay marriage in the state.

NOM also played a pivotal role in passing Proposition 8, the anti-gay measure that yanked back the right to marry from gay and lesbian couples in California. A California gay rights group, Californians Against Hate, has alleged NOM is a political front group for the Mormon Church, whose members, under appeal from church leaders, donated enormous financial and organizing resources towards passage of Proposition 8.