Montgomery County Council member Valerie Ervin is the latest same-sex marriage supporter featured in an ongoing ad Web-based campaign in Maryland.

“It’s important we do everything we can right now to help all working families,” Ervin (D-Silver Spring) says in the ad, released Thursday by Marylanders for Marriage Equality.

It comes on the eve of a key hearing in the Maryland House of Delegates on whether to legalize gay marriage.

Lawmakers from two House committees are scheduled to hear hours of testimony Friday from both supporters, including Gov. Martin O’Malley (D), and opponents.

A similar bill died last year in the House of Delegates after narrowly passing the state Senate.

Ervin is the first African-American woman to serve on the Montgomery County Council. A recent Washington Post poll found a sharp divide on the issue among Maryland Democrats based on race. Among whites, 71 percent support same-sex marriage, while 24 percent do not. Among blacks, 41 percent are supportive, while 53 percent are opposed.

The ad is the 12th in a series that supporters have vowed to continue until votes are taken in the 90-day legislative session.