Democratic presidential candidate Martin O’Malley suggested Sunday that Congress had fallen under the sway of "white racism" and the political force of the National Rifle Assn. in refusing to respond with new laws to a cascade of shooting incidents in recent years.

Speaking before the nation’s mayors, gathered in San Francisco, O’Malley pointed to gun restrictions passed when he was governor of Maryland to ban assault weapons, enforce background checks and tighten permitting procedures -- efforts that have been blocked at the national level by Republicans, and some Democrats, in Congress.

"One of the sad triumphs of white racism is the degree to which it has succeeded in subconsciously convincing so many of us, black and white, that somehow black lives don’t matter," he said. "If the thousands of young men killed by gun violence every year across America were young, poor and white -- rather than young, poor and black -- it is hard to imagine that our Congress would continue to block common-sense measures to keep guns out of the hands of criminals."

"How many acts of violence do we have to endure as a people before we stand up to the congressional lobbyists of the National Rifle Assn.? How many more Americans have to die?" he added, ticking off killings at an elementary school in Newtown, Conn., a theater in Aurora, Colo., and the Navy Yard in Washington, D.C.

O’Malley, a familiar face to the mayors since his pre-gubernatorial tenure as mayor of Baltimore, was the third national Democrat to use the gathering to call for restrictions on the availability of guns in the wake of Wednesday’s mass shooting at Emanuel African Methodist Episcopal Church in Charleston, S.C.