That Bernie Sanders endorsed Hillary Clinton as the Democratic Party nominee for president against presumptive Republican nominee Donald Trump is no surprise to anyone who has paid attention what he said he would do from day one of his campaign. What is surprising is the way went about it which will kill the enthusiasm of his supporters and is a ‘YOOJ’ blow to the political revolution he spent the better part of a year drumming up (quite successfully).

Sanders skillfully handled the post-primary behind-the-scenes wheeling and dealing with the Clinton machine, a skill he honed getting things done in Congress. He had something the Clintons wanted — his endorsement — and used that leverage to extract the most progressive platform in the history of the Democratic Party from the Democratic establishment. Although he was not entitled to any representation on the party’s platform committee, his arch-nemesis and Democratic National Committee chair Debbie Wasserman Schulz conceded one-third of the seats on that committee to people of his choice. Sanders put hardcore progressives like Democratic Socialists of America’s Cornell West, environmentalist Bill McKibben, and Palestine solidarity stalwart James Zogby on the platform committee. They waged a very public and spirited fight on a whole range of issues — $15/hr minimum wage, Palestine, the death penalty, the job-killing Trans-Pacific Partnership (TPP) trade deal, and a slew of other issues. On some issues, they won and on some issues they lost.

The point of fighting over issues in the platform committee was not because the platform is binding on the party (it isn’t), the point was to fight. The struggle was the point. It was a way to continue the political revolution i.e. mass engagement and activism beyond the last primary in Washington, D.C. (and it is only mass engagement and activism that could possibly power any real movement towards a third party in this country).

For weeks, the Sanders campaign has been publicly talking about turning the convention in Philadelphia into a contested convention, a rowdy exercise in democracy marked by issue-based floor votes instead of what the Democratic establishment hoped it would be — a safe, boring Clinton coronation. The official campaign sent out a fund-raising appeal to help Sanders delegates pay the roughly $5,000 necessary for food, lodging, travel, and other expenses associated with the attending the convention since none of them are lobbyists or well-heeled. As per usual, Sanders’ grassroots supporters created their own unofficial website AdoptABernieDelegate.com to pool together all the individual crowdfunding GoFundMe pages people set up to help fund their trips to Philadelphia.

But suddenly and inexplicably, Sanders’ campaign manager and long-time loyalist Jeff Weaver went on With All Due Respect and announced there would be no floor fight over TPP at convention. Now, nearly 1,900 delegates are wondering why the hell should they bother going to Philadelphia if the convention is just going to be a nauseating love-fest for someone that a majority of the American public thinks should have been indicted over her damn emails? People who were planning on attending the multitude of protests and events outside the convention are also having second thoughts for the same reason — why bother?

Sanders has some serious explaining to do and he better do it fast before the millions of Americans he inspired to take action go back to return to their natural state of cynicism about politics. If he doesn’t, Donald Trump will exploit this unexpected opening to drive home his message: the system is rigged and I’m your only hope of changing it in the 2016 presidential cycle.