Sen. Bernie Sanders on Monday urged his supporters to back former rival Hillary Clinton's White House bid, but drew jeers from his supporters as dissent enveloped the opening day of the Democratic Party's convention.
Sanders' followers shouted "We want Bernie" in a show of anger at both Clinton's defeat of him in the presidential nomination race and emails leaked on Friday suggesting the Democratic leadership had tried to sabotage Sanders' insurgent campaign.
For months, Sanders, 74, mounted an unexpectedly tough challenge to Clinton, 68, a former secretary of state, who this week will become the first woman nominated for president by a major U.S. political party.
Sanders complained bitterly during the primary process that the party leadership was working against him. Some of his backers are reluctant to get behind Clinton, seeing her as a member of the Washington political elite who pays only lip service to realizing their goals of reining in Wall Street and eradicating income inequality.
The scenes of booing at the convention in Philadelphia were a setback to Democratic officials' attempts to present the gathering as a smoothly run show of party unity in contrast to the volatile campaign of Republican nominee Donald Trump.
Even before the meeting started, disagreements broke out into the open. At a morning gathering of Florida delegates, Sanders supporters jeered Democratic National Committee chairwoman Debbie Wasserman Schultz, who they accuse of trying to sabotage the campaign of the democratic socialist from Vermont, and who has resigned over the email controversy.
Sanders, speaking later to his delegates in Philadelphia, was booed when he urged supporters to block Trump in the Nov. 8 election by backing Clinton and her vice presidential running mate, U.S. Senator Tim Kaine of Virginia.
"Brothers and sisters, this is the real world that we live in," he said, adding, "Trump is a bully and a demagogue."
Members of the crowd screamed back: "So is Hillary." "She stole the election!" someone else shouted.
While Sanders has endorsed Clinton, the former first lady faces the task of attracting his backers as she battles Trump. The New York businessman pulled ahead in at least one opinion poll on Monday, after lagging Clinton in most national surveys for months. A CNN/ORC opinion poll gave Trump a lead over Clinton, 48 percent to her 45 percent in a two-way presidential matchup.
Trump was formally nominated for president at a chaotic Republican convention in Cleveland last week.
The Democratic National Committee apologized to Sanders on Monday
"On behalf of everyone at the DNC, we want to offer a deep and sincere apology to Senator Sanders, his supporters, and the entire Democratic Party for the inexcusable remarks made over email," the DNC said in a statement.
It said the emails did not reflect the committee's "steadfast commitment to neutrality during the nominating process."
Sanders was among those due to speak on the first evening of the Democratic convention, due to formally open at 4 p.m. Other speakers included First Lady Michelle Obama.