Every time Hillary Clinton and her running mate, Tim Kaine, were mentioned onstage during the first several hours of the convention, a round of boos followed. At different points as different people spoke, Sanders supporters broke into chants of "Bernie! Bernie!" Some delegates shouted "No TPP" in protest of the Trans-Pacific Partnership, a trade deal decried by Republican nominee Donald Trump as well.
In the wake of the outcry, an effort on both the Clinton and Sanders teams was underway to quash any lingering issues, sources said.
Sanders sent a personalized text to his supporters in an effort to quell any remaining tensions and calls for action on the floor tonight. The text read: "I ask you as a personal courtesy to me to not engage in any kind of protest on the floor. Its of utmost importance you explain this to your delegations - Bernie," the text read.
Beyond Sanders' individual actions, Clinton and Sanders whips were working together on the floor to stop and protests. This includes well-known Sanders surrogates like Ben Jealous, the CEO of the NAACP, who spoke on stage this evening.
The fractious start comes days after a leak of Democratic National Committee emails that appeared to show Wasserman Schultz and other committee officials showing favor to Clinton and trying to undercut Sanders' bid.
Shortly after the convention began, the Democratic National Committee apologized to Sanders.
"On behalf of everyone at the DNC, we want to offer a deep and sincere apology to Sen. Sanders, his supporters and the entire Democratic Party for the inexcusable remarks made over email," interim DNC Chairwoman Donna Brazile said in a statement. "These comments do not reflect the values of the DNC or our steadfast commitment to neutrality during the nominating process."
Even that didn't go smoothly: She called the meeting to order but forgot to use the gavel.
The first time Clinton was mentioned during the convention was during the invocation, and while there was a round of cheers, there was also a burst of "Bernie!" chanting that lasted about 20 seconds.
The next speaker faced a similar fate, with chants of "Bernie" and "No TPP" heard.
"I am going to be respectful of you, and I want you to be respectful of me," Ohio Rep. Marsha Fudge said after being interrupted. "We're all Democrats, and we need to act like it."
Maine state Rep. Diane Russell was met with a mix of "Bernie!" and "Clinton!" cheers when she said she is "a proud delegate for Bernie Sanders."
"I want to be clear," she said. "We did not win this by selling out. We won this by standing up. We won this by standing together."
Russell continued, "Whether you support Bernie Sanders or Hillary Clinton, we're all in this together … We will all have a voice in a Clinton administration. We can work together on so much."
Rep. Elijah Cummings, D-Md., gave an address about the work of the Democratic Rules Committee while battling shouts of "No TPP" steadily through his speech.
A group of about eight Michigan delegates formed a silent protest for a portion of Monday night. Some had tape over their mouths saying they were "silenced by the DNC" or signs to that effect. They told ABC News that they plan to hold their signs throughout the night.