Hours after he was interrupted and booed by Sanders supporters during his own address to the convention, the longtime Maryland lawmaker told MSNBC it's time for Sanders to bring his supporters behind Clinton, who is expected to be formally nominated for president later this week.

ADVERTISEMENT

"He has to unequivocally say he supports Hillary Clinton," Cummings said.

Cummings drew the ire of Sanders supporters in part because he chaired a committee that set up the Democratic platform, which does not forbid passage of the Trans-Pacific Partnership trade deal despite objections to the pact from Sanders and other key Democrats.

But Cummings said Sanders, Clinton's chief primary opponent, had got 90 percent of what he wanted in the platform.

"He's got to do it," he said of the need for Sanders to help unify the party by bringing his supporters along. "He's got to get that to his people."

Cummings downplayed the infighting that has been the story of the Democratic convention’s first day.

"These are growing pains," he said, adding that "a lot of these people have never participated in the political process."