Bernie's summer was supposed to be about strengthening his hand for the Democratic convention. But since the California primary, his position has gotten weaker.

BURLINGTON, Vt. — Leverage: it’s the one thing Bernie Sanders’ advisors and aides consistently point to when asked why, exactly, he’s formally staying in the Democratic primary race that he’s lost to Hillary Clinton.

But it's the one thing he’s been bleeding every day ever since he dropped California’s primary by a much wider-than-expected margin last week. Sanders’ summer was supposed to be all about building leverage for the Democratic convention, providing him with a better hand to play as he presses Clinton to accept his policy positions and party reform suggestions. Now, the people closest to him aren’t sure how exactly to get it back.

His first and most prominent endorsers have jumped off the bandwagon, congratulating and in some cases endorsing Clinton — from Sen. Jeff Merkley to Rep. Raul Grijalva, and from the Communications Workers of America to MoveOn.org.Each of the big-name Democrats and groups who steadfastly remained neutral in the primary have flocked to Clinton over the past week, from President Barack Obama to Sen. Elizabeth Warren to the AFL-CIO. Even Sanders' highest-profile congressional endorsee, Nevada’s Lucy Flores, lost her primary bid on Tuesday despite his cash injection into her campaign.

Yet on Thursday night, speaking to over 200,000 viewers who tuned into his live-streamed video address, Sanders vowed to press on — pledging to fight to defeat Donald Trump but refusing to formally back Clinton and insisting his army of supporters isn’t going anywhere.