Maryland Gov. Martin O’Malley’s signature on an historic marriage equality bill is hardly dry, but he is already preparing for a referendum, the Washington Post reports. He signed the legislation last Thursday.

Maryland Gov. Martin O'Malley

“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 campaign missive Friday.

He was seeking support from the Marylanders for Marriage Equality. That coalition was key to passing the legislation.

“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 said.

Opponents began collecting the nearly 56,000 signatures needed before the signing ceremony. If they’re collected, marriage equality would be on the November ballot. The law takes effect in Jan. 2013.