"The major political task that we face in the next five months is to make certain that Donald Trump is defeated and defeated badly," Sanders said in a much-anticipated live-stream address. "And I personally intend to begin my role in that process in a very short period of time."
Sanders did not offer details on how he plans to fulfill that role.
Much of the video amounted to a version of Sanders' standard stump speech, and he encouraged his legions of followers to run for local office.
He once again pledged to take his bid all the way to the convention. And he described his differences with Clinton as "strong" but limited.
"It is no secret that Secretary Clinton and I have strong disagreements on some very important issues. It is also true that our views are quite close on others," Sanders said. "I look forward, in the coming weeks, to continued discussions between the two campaigns to make certain that your voices are heard and that the Democratic Party passes the most progressive platform in its history and that Democrats actually fight for that agenda."
The Vermont senator vowed to take his campaign's "energy" into the Democratic National Convention next month. But Sanders campaign manager Jeff Weaver told
Bloomberg News earlier Thursday that the campaign was no longer actively lobbying superdelegates.
Fight with DNC continues
Sanders' presidential campaign is winding down -- but his fight with the Democratic National Committee is just getting started.
The Vermont senator has called for the ousting of leadership from the convention committee level up to the top -- publicly insisting that DNC Chairwoman Debbie Wasserman Schultz be replaced. And his campaign wants two well-known Democrats removed from key posts at the national convention in Philadelphia next month.
"I do believe that we have to replace the current Democratic National Committee leadership," Sanders told reporters in Washington Tuesday as the last Democratic primary voters went to the polls. "We need a person at the leadership of the DNC who is vigorously supporting and out working to bring people into the political process."
Sanders has publicly clashed with Wasserman Schultz throughout the campaign, including a spat over the number of debates scheduled that led to one of his congressional backers, Hawaii Rep. Tulsi Gabbard, quitting her post at the DNC.
He also sent a letter last month to the committee calling for the removal of two Democrats from their convention leadership positions: Connecticut Gov. Dannel Malloy, who co-chairs the Platform Committee, and former Massachusetts Rep. Barney Frank, co-chairman of the Rules Committee.
The DNC swiftly dismissed the request.
Frank has spoken out against Sanders, writing in July 2015 that Sanders' campaign was a threat to Clinton's chances in a general election and "wishful thinking is no way to win the presidency." Malloy has been critical of Sanders' record on gun control.
A spokeswoman for the DNC said the committee has not received any further requests from either campaign over personnel, and a spokeswoman for Malloy said the governor has not heard any more about the matter.
"They have already tried this and it was ruled out of order," said Leigh Appleby, communications director of the Connecticut Democratic Party. "Gov. Malloy looks forward to chairing the committee in a fair manner and putting forward a platform that stands in stark contrast to Trump and his hateful, divisive policies."
Frank, for his part, downplayed the significance of the spat, saying he believes the animosity will calm down.
"I think that that has sort of faded," Frank said.
But he did say the convention would include "healthy debate" more than in previous cycles.
"I think there has been more differences here than in previous ones, but I think with Donald Trump being himself so dangerous, that the focus will be more on getting together to in in November," Frank told CNN. "There will be issues, there probably will be more debates, three or more platform debates and this issue of superdelegates."
Still, Sanders is giving no indication that he's letting up the pressure.
Asked if the campaign stood by the request to remove Malloy and Frank and if they would raise the issue with the Clinton campaign, Sanders spokesman Michael Briggs simply said "yes."
And Sanders on Tuesday used his news conference in Washington to spell out a list of his demands for the DNC platform and reforms.
"We are going to fight as hard as we can to create a Democratic Party which represents the working families and the low-income people in this country," Sanders said. "The time is long overdue for a fundamental transformation of the Democratic Party."
Among the demands he made publicly on Tuesday were opening primaries to independent voters, same-day registration and doing away with super delegates that aren't bound by voters' ballots. And several points of conflict
are expected to emerge between Sanders' and Clintons' camps on the platform, including on the minimum wage, fracking, trade and Wall Street regulation.
Clinton and Sanders met Tuesday night in Washington as well. The two campaigns put out very similar statements after the meeting, saying the candidates and their aides met to talk about unifying the party, beating Trump and "progressive" ideas.
The senator is likely to call for a roll call vote at the convention, according to a person close to the campaign, and on Tuesday he ignored a question from CNN's Jeff Zeleny on Tuesday about whether he'd place Clinton's name into nomination as she did for Barack Obama in 2008.
A veteran of the primary process said lingering hard feelings are nothing unusual for the end of a campaign. But former Obama adviser and CNN contributor Dan Pfeiffer said that it's up to the candidates to set the tone going forward.
"It takes a long time for bad blood to go away," Pfeiffer said. "A lot of Obama and Clinton folks harbored resentments until well after the election was over. But both the President and Secretary Clinton sent pretty clear signals that they wouldn't tolerate any bad behavior, and pretty quickly the urgency of winning the general election forces everyone to put that aside."