Here’s more evidence that the battle over Maryland’s expected referendum on same-sex marriage is ramping up: The lead group lobbying for the legalization of gay nuptials has hired a campaign manager.

Lt. Gov. Anthony Brown (D) watches as Maryland Gov. Martin O'Malley (D) shakes hands with Sarah E. Reece, of the National Gay and Lesbian Task Force at the same-sex marriage bill signing in Annapolis. (Photo by Linda Davidson/The Washington Post)

Levin has previously served as the campaign manager for several Democratic congressional candidates, including Tammy Duckworth in Illinois and Mary Jo Kilroy in Ohio. His resume also includes work for some left-leaning advocacy groups and 2004 presidential candidate Howard Dean.

Same-sex marriage opponents are busy gathering signatures to force a public vote on a bill signed last month by Gov. Martin O’Malley (D) that would legalize gay nuptials in Maryland as of Jan. 1.

Both sides expect the petition effort to be successful, giving voters statewide the final say on the matter.

In a statement Wednesday, O’Malley praised Levin, saying his “campaign experience will be invaluable.”

 “I am confident voters this fall will come down on the side of human dignity,” O’Malley said. “All of our children deserve the opportunity to be protected equally under the law.”

Marylanders for Marriage Equality also announced Wednesday that Sultan Shakir, who led this year’s legislative effort, will become political director for the referendum.