Aamer Madhani, and Kevin Johnson

USA TODAY

PHILADELPHIA— With rival Bernie Sanders vanquished, presumptive Democratic nominee Hillary Clinton faces new competition as she tries to win over some of the most passionate backers of the Vermont senator’s campaign: Green Party candidate Jill Stein.

Hundreds of pro-Sanders demonstrators marched through Center City on the first day of the Democratic National Convention on Monday, chanting “Bernie or Jill, No Hill,” raising fresh questions about whether Clinton will face a bleed of Sanders' most devoted backers if they bail on the Democratic Party and back the presumptive Green Party nominee. Hundreds more showed up to hear Stein address demonstrators at FDR Park near the Wells Fargo Center, where this week’s Democratic convention is being held. Stein has framed herself as the Plan B for the “Bernie or Bust” crowd.

In her address at the Monday evening rally, Stein, a physician from Massachusetts and longtime Green Party activist, accused the Democratic National Committee of sabotaging the Sanders campaign, a reference to thousands of emails leaked last week that showed senior members at the committee sought to undercut Sanders campaign. One official even suggested raising questions about whether Sanders, who is Jewish, was in fact an atheist.

The release of the emails by Wikileaks led DNC chairwoman Debbie Wasserman Schultz to resign from her post on the eve of the convention's start, laying a dark cloud over Clinton in her efforts to unify the party following her tough nomination battle with Sanders.

“We are leaving behind the corruption, the backstabbing and the lies,” Stein told the protesters. “They have said they said bad things about Bernie and have apologized. They have said much more than bad things. They sabotaged a revolutionary campaign.”

Stein won just 470,000 votes nationally as the Green Party’s 2012 presidential nominee. But many diehard Sanders supporters who came to Philadelphia to protest this week’s convention say they’ll shift their support to Stein unless Sanders disavows the endorsement he gave Clinton after it became clear he would fall short of winning the Democratic nomination.

In Philadelphia on Monday, Sanders again reiterated that the party must support Clinton in November to defeat Republican nominee Donald Trump, who he blasted as a “bully and demagogue” who made bigotry the cornerstone of his campaign.

But on the streets of Philadelphia, where thousands of self-described “Berners” have descended this week to express their frustration with the Democratic Party, the idea of throwing their support to Clinton is a non-starter.

Some in the "Bernie or Bust" crowd suggest the idea of a Hillary Clinton presidency is as unpalatable — perhaps even more so — than the idea of a Donald Trump presidency.

A CNN/ORC poll published Monday suggests the presence of Stein and Libertarian candidate Gary Johnson in the race could have potential ramifications on the outcome. The poll, which was conducted over the weekend after Trump accepted the GOP nomination at the Republican convention, showed Trump leading Clinton nationally by a 44% to 39% margin, with Johnson taking 9% of the vote and Stein taking 3%. The poll, however, does not detail how the candidates fare in battleground states.

The last time the Green Party had a significant impact on a presidential race was in 2000, when Ralph Nader drew 2.9 million vote nationally and faced blame for playing the role of the spoiler who helped deliver Florida to George W. Bush in his race against Vice President Al Gore. This time around, the Green Party is aiming to get on the ballot in 47 states.

Jim Cavanaugh, a Sanders supporter who said he will vote for Stein, pushed back against the notion from Democrats that a vote for Stein was a spoiler vote. He said he would not vote out of fear.

“The common assumption is that she is the lesser of two evils, and I think she is very evil,” said Cavanaugh, of Norristown, Pa., who is critical of her foreign policy and environmental records. "Trump is a wild card. We know the evil she is."

Cornel West, the activist and professor who supported Sanders in the primaries, earlier this month offered perhaps the highest profile endorsement of Stein, calling her the “only progressive woman in the race.” West served on the Democratic National Convention platform committee, but skipped the final voting in protest.

West, who attended Stein’s rally on Monday, said in an interview that the Democratic Party has become a "corporately dominated" organization that is at risk of losing many Sanders supporters to the Green Party.

“Big money is running things,” West said.

Gayle Madeira, 46, of New York, took part in Monday’s rally, holding a sign that read “Never Hillary” and “I will not vote for lies and security breaches.” In the past, Madeira said she has always backed Democratic candidates, but in November she plans to cast her ballot for Stein.

“Both Hillary and Trump to me are equally bad,” Madeira said. “The Democratic platform is better, but the Democratic platform is not binding. And Hillary, as we have seen by her record, is a compulsive liar and she is going to do whatever she wants to.”

'Hillary Clinton must become the next president,' Sanders tells convention

Other Sanders supporters said they still feel passionately about the Vermont senator, but they could not follow his call to back Clinton.

Protester Don Johnson said he’d “follow Bernie anywhere,” but voting for Clinton was a line he would not cross. Johnson, a U.S. citizen who lives in Thailand, added that Stein represents the real alternative now that Sanders has endorsed Clinton.

"We just can't go with him on this," said Johnson, who timed his trip to the U.S. to be part of the protests. "I think there are a lot of people who feel the same way. Just look around."

During the first night of the convention, plenty of effort was made to soften the blow to Sanders supporters and try to ease them into the Clinton tent.

Protesters take to streets in Philly in intense heat, thunderstorms

Speakers like Sen. Corey Booker, of New Jersey, and Sen. Bob Casey, of Pennsylvania, also underscored Clinton’s recognition of the widening disparities between the nation’s rich and poor — an issue that was at the cornerstone of the Sanders campaign — and one the senators say Trump is blind to.

The comedian Sarah Silverman, who was an outspoken advocate of Sanders, was given a prominent speaking spot in which she credited Clinton with hearing the passion of Sanders' backers and implementing many of their concerns into the Democratic platform.

“Hillary is our Democratic nominee, and I will proudly vote for her,” Silverman said. “I will vote for Hillary with gusto as I continue to be inspired and moved to action by the ideals set forth by Bernie, who will never stop fighting for us. I am proud to be part of Bernie’s movement, but part of that movement is making absolutely sure that Hilary Clinton is our next president of the United States."

When Silverman was greeted by some boos from Sanders supporters in the convention hall, she retorted, "To the Bernie or Bust people, you are being ridiculous."

In her remarks, Stein pushed back at the notion that Sanders' backers were obligated to back Clinton and suggested they had an opportunity to send the Democratic Party a message.

"Forget the lesser evil,” Stein told them. “Vote for the greater good.”

Contributing: Grant Miller