Raskin attributed the disappointing outcome in large part to a "fierce grassroots campaign" by religious groups opposed to marriage equality. He said opponents seemed spurred to action by the success in the senate, which approved the bill by a 25-21 vote two weeks ago without protracted debate.

"A number of delegates told me they were planning to move in a positive direction but there were just tons of robocalls coming into their district," he said. "I think the opponents were stunned by our success in the senate. They called in the heavy artillery from around the country."