Maryland Gov. Martin O'Malley, right, hugs House Speaker Michael E. Busch after the House passed a same-sex marriage bill. (Patrick Semansky/Associated press)

“I wish I could tell you that we’ve won the battle; that our State is more just today than it was yesterday,” O’Malley said in a solicitation sent to his campaign supporters Friday. “But the reality is, there are enough people who oppose equality, that the future of marriage equality is in jeopardy.”

Even before Thursday afternoon’s signing ceremony, opponents of the legislation had started collecting signatures to force a public vote on the measure in November — a campaign aimed at derailing the new law, which is scheduled to take effect in January.

The months-long fight is widely anticipated to draw national attention and resources from both sides, as evidenced by a statement issued Friday by Brian Brown, president of the National Organization for Marriage.

“The Maryland same-sex marriage legislation is a meaningless, symbolic act,” Brown said. “The people of Maryland, not politicians, will have the final say on marriage. And they will overturn this act of the General Assembly.”

O’Malley’s solicitation seeks contributions for Marylanders for Marriage Equality, the coalition that successfully lobbied for the bill’s passage.

“Make no doubt about it, this issue will go to referendum and the other side will have the money and resources to fight against it,” O’Malley’s e-mail says. “We can stop them but we need to start early. Join me and donate $10, $20, $50 or even more to protect human dignity.”