The National Organization for Marriage, the leading group opposing same-sex marriage in the U.S., has set its sights on Maryland and D.C., where it plans to pour in money and resources to overturn D.C.’s same-sex marriage law and prevent Maryland from passing one.

The group was scheduled to hold a rally Wednesday night in Annapolis at the state capital building to demand that lawmakers reject a gay marriage bill that has been introduced in the Maryland Legislature.

NOM has scheduled an Aug. 15 rally in D.C. calling for a ballot measure to overturn the city’s same-sex marriage law, but it has yet to announce the time or location for the event.

The Annapolis and D.C. rallies are part of the group’s “Summer for Marriage Tour 2010,” that includes a series of 20 rallies “encouraging supporters to stand up for marriage,” according to an announcement on the NOM website. Staff and volunteers for the group are traveling by bus to the rallies, which began in Maine on July 14.

“We’re excited to get on the road and meet people face-to-face, sharing with them the importance of marriage and how critical the future of marriage is to our country,” said Brian Brown, NOM’s executive director. “We need Americans to rally behind marriage as the union of one man and one woman and tell the courts and state legislatures that marriage matters.”

Bishop Harry Jackson, the Maryland minister who is leading the fight against D.C.’s same-sex marriage law, was scheduled to join Brown as one of the speakers at the Annapolis rally on Wednesday. Other speakers were to include members of the legislature from Baltimore and Prince George’s County who are expected to lead the fight against a Maryland gay marriage bill.

Morgan Meneses-Sheets, executive director of the statewide LGBT group Equality Maryland, said the group was to hold a series of its own events Wednesday night throughout the state. But she said the group was not planning a counter protest at the state capital in Annapolis.

“We are asking our people not to engage them,” she said of the NOM rally participants. “It’s not in our best interest for us to be there. It’s just a PR event for them.”

Instead, Meneses-Sheets said Equality Maryland had organized teams of volunteers to distribute postcards in Baltimore and several counties throughout the state, including Prince Georges and Montgomery Counties, in support of the state gay marriage bill. Those accepting the postcards were to be asked to mail them to their state representatives in a show of “growing support” for the marriage bill, she said.

Also scheduled for Wednesday night was a “Pride in Faith” meeting in Baltimore, where members of the clergy supportive of same-sex marriage would discuss ways to advance the same-sex marriage bill in the legislature.

The NOM 20-city tour was scheduled to end with the Washington, D.C. rally. Local D.C. groups have yet to announce plans on how they might respond to the D.C. rally.

The D.C. Court of Appeals ruled 5-4 last week against a lawsuit filed by Bishop Jacking seeking to force the city to hold a voter initiative calling for overturning the D.C. Marriage Equality Act, which legalized same-sex marriage in the District.