Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

PHILADELPHIA — Democrats’ hard-won and still unset party unity will be tested on the first day of their National Convention on Monday as Bernie Sanders takes the stage while his delegates threaten disruptions — even after the ouster of the party’s chairwoman a day earlier.

Democrats are hoping to draw a sharp contrast with the discord Republicans experienced during their own convention last week in Cleveland, and polls show the Democratic voters are lining up behind presumptive nominee Hillary Clinton. But a vocal minority of objectors still threaten the fragile order.

Monday is all about Sanders' wing of the party, even as the official focus is on Clinton’s commitment to families.

The speaker lineup reflects a clear effort by the Democratic National Committee and Clinton’s campaign to make Sanders’ supporters feel heard, with slots for many of his top supporters and ideological allies, in addition to the Vermont senator himself.

Beyond Sanders, the keynote address will be delivered by Sen. Elizabeth Warren, the liberal darling beloved by many Sanders voters, even though she did not endorse a candidate in the primary.

Sen. Jeff Merkley, Sanders’ only endorser in the upper chamber, will also speak — as will Reps. Keith Ellison and Raul Grijalva, the co-chairmen of the Congressional Progressive Caucus and Sanders’ first two backers in Congress.

Meanwhile, Democrats will also hear from First Lady Michelle Obama and New Jersey Sen. Cory Booker, who was on Clinton’s shortlist for the vice presidential slot. Other speakers include a string of organized labor leaders, including ALF-CIO head Richard Trumka.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Democrats hope the strong lineup will draw a sharp contrast with the Republican National Convention, which many party dignitaries avoided, underscoring lingering divisions in that party over Trump’s nomination.

But Democrats may find their own ideological seams exposed Monday, something Trump is eager to exploit.

“The Democrats are in a total meltdown,” Trump said on Twitter, while goading Sanders supporters. “Looks like the Bernie people will fight. If not, their BLOOD, SWEAT AND TEARS was a total waste of time.”

Even by Sunday, the presence of Sanders supporters was strongly felt on Philadelphia's sweltering streets, with organizers expecting much larger protests here than in Cleveland last week.

The party abruptly ousted Chairwoman Debbie Wasserman Schultz on Sunday, who had become loathed by Sanders’ wing after apparently favoring Clinton in the Democratic primary Wasserman Schultz was supposed to be neutrally refereeing.

The move was so unexpected that the credentials hanging from the necks of the thousands of delegates and journalists here will still have her name printed at the top. “2016 Democratic National Convention,” they read. “Debbie Wasserman Schultz, DNC Chair.”

A supporter of Sen. Bernie Sanders cools off in a fire hydrant during a protest march ahead of the DNC in Philadelphia on Sunday. Bryan Woolston / Reuters

Democrats hope her removal will help clear away lingering baggage from the primary. “It was clean up day,” said one Democratic official.

Indeed, upon hearing the news, Ben Jealous, the former president of the NAACP and a top Sanders surrogate, instantly endorsed Clinton while appearing live on MSNBC. “This rips off the Band-Aid, it lets us move on, it lets our party begin to heal, and it’s what we have to do when we have only 100 days left to beat Donald Trump,” he said.

Sanders himself said: “Debbie Wasserman Schultz has made the right decision for the future of the Democratic Party.”

Still, Wasserman Schultz plans to step down only at the end of the convention, and she will take the stage Monday to formally gavel in the convention. The question is not if she will be booed, but how loudly.

“It doesn't satisfy this Bernie delegate,” said Norman Solomon, a California Sanders delegate who helped organize a national network that includes most of Sanders’ 1,900 representatives to the convention. “The sacrificial official does not change the essence of the issue.”

Solomon said he appreciated Monday’s speaking lineup, but dismissed it as “symbolic gestures.”

Many Sanders delegates, who like all delegates have to pay their own to way to convention, said they didn’t shell out thousands of dollars in order to see Clinton's coronation.

“We're going to make as much noise as possible. When issues come up that we disagree on, we're going to be loud,” said Allen Roskoff, a New York Sanders delegate and LGBT activist. “We may be drowned out by the Hillary people, but have to make ourselves heard.”

Karen Bernal, a leader of California’s delegation, said many Sanders delegates have no interest in causing problems. “There's a whole spectrum,” she said.

But even a small, vocal minority could cause headache and distract from Democrats’ carefully choreographed show of unity. During the 2012 convention, a mere handful of delegates demonstrating on Middle East issues interrupted what had otherwise been a flawless convention.

Moumita Ahmed, a New York delegate and the founder of the group Millennials for Bernie, said delegates are coordinating with protesters outside the convention hall and were heartened by anti-Trump forces’ demonstrations on the floor of the Republican convention last week.

“I thought what they did was really bold and definitely something we're all taking lessons from,” she said.