The vast majority of House Democrats endorsed Clinton's candidacy early in the primary process, but Sanders was invited to attend the weekly meeting as a courtesy extended to all presidential candidates. When Clinton appeared last month, she was applauded and praised for her commitment to help Democrats regain control of Congress this fall.
Many Democrats have been reluctant to publicly criticize Sanders for continuing his campaign because they want to ensure that the supporters he activated through the long primary contest will come out and vote for the Democratic ticket in November. But some members let out their frustration with the Vermont senator Wednesday morning, with one member calling Sanders' appearance before the caucus a "total display of self-obsession."
During the discussion, Sanders told the group "the goal is not to win elections" and took a dramatic pause, before adding that the aim was to win the battle of ideas, according to multiple sources in the room.
A series of Democrats pressed Sanders to say when he would end his efforts and endorse Clinton and work to unite the party. But after Reps. John Garamendi of California, Mark Takano of California and Joyce Beatty of Ohio, failed to get a concrete answer from the senator, roughly a dozen members booed him inside the room.
During one exchange several members chanted "timeline, timeline" when Sanders' sidestepped a question on when he would back Clinton.
Asked about his message to the House Democratic Caucus, Sanders said as he left the session, "We've got to get a large voter turnout. If we get a large voter turnout, Democrats will regain control of the Senate and I believe they're going to take the House back."
House Democratic Caucus Chairman Xavier Becerra, who presided over the meeting, said he never heard any boos during the session, but downplayed the dissent, saying the discussion was "animated." He said members did focus on the need to unify, and Sanders informed House Democrats that Clinton was announcing her support for his approach on college affordability.
The number two House Democrat, Rep Steny Hoyer, told reporters he was sitting in the front row during the meeting with Sanders and didn't hear anyone booing. He said Sanders told Democrats he would do all he could to defeat Donald Trump this fall and he took that to say he was backing Clinton. He described some members as being "anxious" about Sanders' answer about when he would endorse Clinton.
Virginia Rep Gerry Connolly took issue with some descriptions of the meeting on Twitter, saying, "Bernie was respectfully received by Caucus. Some disagreements, yes, but a friendly venue" and "Sanders was reflective and thoughtful in responses. Expressions of disagreement are NOT booing."