Lucas Jackson / Reuters

Bernie Sanders so far refuses to give up his fight for the White House. But in yet another sign that his campaign for president has stalled out, one of the Vermont senator’s most loyal and prominent backers has announced his support for Hillary Clinton.

Raul Grijalva, an Arizona Democrat and the first member of Congress to endorse Sanders, explained his reasoning in a statement:

With voting completed in the final Democratic Primary, it is now time for the Democratic Party to unify. For all of us who supported Bernie from the beginning, whether we considered ourselves progressives or independents or just Americans tired of being on the outside looking in, the most important thing now is to beat Donald Trump in November. To use a word that’s been thrown around a lot lately, now is the time to unify. […]

Hillary Clinton has the capacity and the instincts needed to carry forward what has been started. I support her and will do what I can to help ensure her victory. I firmly believe that her victory will only come when she and the Democratic Party articulate the themes this movement [created by the Sanders campaign] has so powerfully expressed.

That’s an excerpt from a much longer set of remarks from the representative, reported by NBC News’ Danny Freeman on Twitter. The declaration attempts to walk a very fine line. It emphasizes that the ideals and promises at the heart of Sanders’s campaign have widespread support and must be taken seriously by the next president, while at the same time conceding that the next president will not, in fact, be Sanders.

Many Sanders supporters, resigned to the fact that it now looks impossible for their candidate to win the White House, must settle for the next best alternative and hope that Clinton will champion the causes near and dear to the senator. It would be overly simplistic to describe Grijalva’s remarks as a defection. Even in shifting support to Clinton, he wants to push her to embrace the Sanders agenda. “It won’t be enough to just accept the merit of his ideas,”Grijalva said. “This is in no small part Bernie Sanders’ party also. His team, his supporters and his movement must—and will—be integrated into the future of the Democratic Party at every level.” He warned: “Unity will not be realized if the millions of voters who supported Bernie Sanders feel taken for granted.”

Ultimately, however, there is no guarantee that the former secretary of state will take up that mantle. Still, to win in November, Clinton cannot afford to alienate the voters who have stood by Sanders. Her campaign is undoubtedly aware of that and is making an effort to act conciliatory. Earlier in the week, Sanders laid out a series of demands, ranging from a call for “the most progressive platform ever passed by the Democratic Party” to changes to the presidential nominating process. After Sanders lost the final Democratic primary in Washington, D.C., on Tuesday, Clinton met with him to discuss what comes next. A spokesperson for Sanders called the meeting “a positive discussion” in a statement, noting that “the two discussed a variety of issues where they are seeking common ground: substantially raising the minimum wage, real campaign finance reform, making health care universal and accessible, making college affordable and reducing student debt.” But who’s to say Clinton won’t endorse the ideas Sanders has championed only to retreat from them later?

For now, Sanders seems to believe the best way to push Clinton in the direction he wants to see her take the party is to remain in the race. The longer he does so, however, the more he risks losing leverage. Grijalva’s declaration of support for Clinton is a painful reminder of the downward trajectory of the campaign. Not long ago, Jeff Weaver, Sanders’s campaign manager, vowed to spend the weeks leading up to the Democratic National Convention, which will take place next month, attempting to win over party leaders known as superdelegates.  The campaign no longer appears to be actively pursuing that strategy. Grijalva was one of the few superdelegates to support Sanders. Now the campaign has lost even him.

Tonight, Sanders is expected to lay out the next steps for his revolution in a video address from Burlington, Vermont. His campaign has already signaled that he is unlikely to drop out. A spokesperson for the campaign told Bloomberg on Tuesday that Sanders would not exit the race “today, tomorrow, or the next day.” The fact that he has so far stubbornly stuck in the race despite the fact that primary-contest voting has drawn to a close, with Clinton as the clear winner, is a testament to how much Sanders wants to see the changes he is calling for enacted. At the same time, it has become less clear how much leverage he actually has. If even his most ardent supporters decide to support Clinton before Sanders officially quits the race, his ability to wield influence over the party and the presidential race seems poised to diminish even further.

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