Democratic presidential hopeful Martin O’Malley called on South Carolina leaders Sunday to "retire" the Confederate battle flag from their capitol grounds and urged Congress to move forward with “common-sense” gun-control measures in the wake of last week’s church shootings in Charleston.

The comments from O’Malley, a former Maryland governor, came during an appearance in San Francisco at a meeting of the U.S. Conference of Mayors. O’Malley, a former mayor of Baltimore, pledged that he would “rebuild the heart of America’s cities” if elected and noted that it had been 86 years since a U.S. mayor had served as president.

O’Malley, speaking to the group from the same lectern that the Democratic front-runner Hillary Rodham Clinton used on Saturday, said family members of the Charleston shooting victims had voiced forgiveness for the suspect and “let go of their anger.”

"Is it really too much to ask the state government officials of South Carolina to retire the Confederate flag to a museum?” O’Malley asked during a speech that was live-streamed on the mayoral organization’s Web site.

The Confederate flag flew over South Carolina’s capitol dome until 2000, when it was moved to a Civil War memorial on the grounds as part of a bipartisan compromise. A debate over the flag's fate has been rekindled by the fatal shootings of nine African Americans by a suspect with a history of anti-black views who has been photographed with the flag.

O'Malley seemed unaware of the 2000 compromise, saying in his speech that it was "a terribly jarring and callous sight" in the days following the shootings to see "the American flag at half staff, while above it it full staff over the state capitol of South Carolina flew a Confederate flag."

During his remarks, O’Malley, who lags behind Clinton and Sen. Bernie Sanders (I-Vt.) in Democratic primary polls, also questioned why Congress has "blocked" what he called common-sense measures to reduce gun violence.

“The most poisonous force in American politics today is not the bad people who do bad things,” O’Malley said. “It is the good people who do nothing. . . . 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 and the mentally ill."

He reiterated a call, made in recent days, to pass a national ban on assault weapons, to put in place stricter background checks for gun purchases and to take steps to prevent “straw purchases” of guns, such as fingerprinting requirements. Similar measures were passed on a state level in Maryland in 2013 at O’Malley’s urging.

O’Malley, who served as Baltimore’s mayor from 1999 until he became governor in 2007, made reference to the rioting in his city in April following the death in police custody of an African American man. He lamented the economic conditions of many urban areas and promised “a new agenda to rebuild America’s cities.”

The fight over a Confederate emblem

COLUMBIA, SC - JUNE 27: Demonstrators protest at the South Carolina State House calling for the Confederate flag to remain on the State House grounds June 27, 2015 in Columbia, South Carolina. Earlier in the week South Carolina Gov. Nikki Haley expressed support for removing the Confederate flag from the State House grounds in the wake of the nine murders at Mother Emanuel A.M.E. Church in Charleston, South Carolina. (Win McNamee/Getty Images)