Sen. Bernie Sanders urged supporters to rally behind Hillary Clinton at the Democratic convention, but ardent followers who marched for hours in punishing heat Monday and planned to do so again seemed intent on keeping his upstart campaign alive.

“Based on her ideas and her leadership, Hillary Clinton must become the next president of the United States,” Sanders said. “The choice is not even close.”

Sanders encouraged his supporters to fall in line with Clinton after dozens were cited for climbing barricades outside the convention. Many pro-Sanders demonstrators expressed disgust with party leaders after leaked emails suggested they had favored Clinton over the Vermont senator during the primary race.

Another series of protests and rallies was planned for Tuesday, the anger reflecting the rift inside the Democratic Party and the convention hall itself between Sanders’ supporters and Clinton’s. Debbie Wasserman Schultz resigned as Democratic Party chairwoman Sunday over leaked emails suggesting that the supposedly neutral Democratic National Committee played favorites during the primaries by siding with Clinton and bad-mouthing Sanders.

As Sanders’ supporters marched 4 miles from City Hall to the convention site Monday afternoon, they chanted “Hey, hey, ho, ho, the DNC has got to go!” and carried signs reading, “Never Hillary,” ”Just Go to Jail Hillary” and “You Lost Me at Hillary.”

Police moved metal fences into place as tensions mounted outside the Wells Fargo Center, and closed the nearest subway station to arriving trains. Fifty-five people were issued citations as they tried to breach police barricades at the edge of the security zone surrounding the convention, police said.

Destine Madu, a protester from Maplewood, New Jersey, said it doesn’t matter if Sanders is calling on his backers to support Hillary Clinton.

“He’s like a Moses,” she said. “He led us to the promised land.”

Deborah Armstrong, of Spokane, Washington, said she and her husband went bankrupt because of his health problems, which required a heart transplant.

“I’m Bernie or bust,” she said. “I’m not going to have Trump held up to our head like a gun.”

The demonstrators espoused a variety of causes, including economic justice, socialism and marijuana legalization. With Sanders out of the race, some of them were backing Green Party candidate Jill Stein.

The four-day convention is far removed from City Hall and the skyscrapers of Center City.

In contrast, the Republican convention last week in Cleveland was held in a bustling part of the city. A heavy police presence and fewer than expected protesters helped authorities maintain order. Only about two dozen arrests were made.

(AP)