Bernie Sanders spoke to Democratic members of the House of Representatives on Wednesday but was reportedly booed as he attempted to explain that his endorsement of presumptive nominee Hillary Clinton might not fit into an easy timeline and that transforming the nation is about more than one election.

While providing anonymity to all of its sources, Politico reported how "one person inside the room" said there were "boos from lawmakers" while Sanders was addressing questions about endorsing Clinton.

One unnamed "senior Democrat" described being personally frustrated that Sanders used the meeting to talk about the central issues of his historic campaign while refusing to simply say when Clinton would receive his blessing publicly. "It was frustrating because he's squandering the movement he built with a self-obsession that was totally on display," the individual said.

Rep. Gerry Connolly (D-Va.), who was present during the meeting, took issue with the version of events offered by Politico's sources, writing on Twitter:

.@politico story is false. Bernie was respectfully received by Caucus. Some disagreements, yes, but a friendly venue — Gerry Connolly (@GerryConnolly) July 6, 2016

Sanders was reflective and thoughtful in responses. Expressions of disagreement are NOT booing — Gerry Connolly (@GerryConnolly) July 6, 2016

Sanders also disputed the reporting by Politico, telling CNN's Wolf Blitzer during a midday interview that "by and large the response was pretty good. There were some people who were in disagreement."

Blitzer asked if he heard actual booing. "I don't know," Sanders shrugged in response. There were, he added, "a few people... discontented."

In its reporting, CNN cited three Democrats who said there was "a group of members booing [Sanders] at one point." The news outlet reported:

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.

Strikingly, of the available reporting, only those who requested or received anonymity from journalists reported hearing boos, while all those identified, including Rep. Steny Hoyer (D-Md.) and House Democratic Caucus Chairman Xavier Becerra (D-Calif.), both of whom spoke to CNN, said they did not.

Meanwhile, the Huffington Post offered this account of the contentious portion of the meeting, reporting that things got increasingly "testy" when the "topic turned from policy to politics":

At some point during the question-and-answer session, members began asking Sanders for a timeline for when he would endorse Clinton. Some began chanting the word “timeline.” Rep. Sanford Bishop (D-Ga.) was yelling from the back of the room, asking him when he’d endorse. Sanders repeatedly declined to offer a specific date, which resulted in some booing from the members. “How do we unite?” asked Rep. Joyce Beatty (D-Ohio), according to the high-ranking aide. “You are the person who has me the most frustrated.” Beatty’s office declined to comment, citing the off-the-record rules of the meeting. Sanders eventually responded that the goal was not to win elections. He paused at this juncture, at which point came the boos. “The goal is to transform America,” he said. The Sanders aide said that members in the room applauded at that point. Leaving the meeting, Sanders spoke briefly to reporters. “My message was a simple message: We have got to fight for the needs of the middle class and working families of this country,” he said. “We got to get people involved in the political process, we got to get a large voter turnout, and if we have a larger voter turnout, Democrats will regain control of the Senate and I believe they’re gonna take the House back.”

Throughout the rise of his unlikely presidential run, there has been widespread recognition that serious tensions exist between the so-called "Establishment" order of the Democratic Party, represented by Clinton and her backers, and more progressive elements drawn to the vision of the broadly-framed "political revolution" articulated by Sanders.

If the reporting on Wednesday's meeting is an indication, it seems that even as the race winds down and the Democratic National Convention approaches, those tensions may still be a long way from being resolved.