Although the numbers game was always a daunting nemesis, up until tonight Bernie Sanders had been able to declare enough electorate victories to keep morale within his campaign elevated and to keep his supporters hopeful that their candidate's declared political revolution would come to fruition. All of that ended tonight, with an evening that was always likely to be Sanders's political Waterloo but which wound up being even worse for him than anyone could've imagined. With Hillary Clinton's apparent sweep of states in both the South and the Rust Belt -- which Sanders was counting on to prove that Clinton's victories were largely regional -- and with her dominant victories in three of those states, she's secured for herself a situation where both time and the delegate math are on her side and present a problem that's now all but insurmountable for her opponent.
Going into tonight, Bernie Sanders needed to win 54% of the remaining pledged delegates to be able to claim the nomination. That would've meant an eight point victory in almost every pivotal upcoming state. As Vox details, what he couldn't afford was a blow-out by Clinton in any of the six remaining states that carried with them half the untaken delegates in the contest, but tonight that's what he got: Clinton routs in Ohio and Florida (and victories everywhere else). True, as Sanders die-hards will say, New York and California and their delegate-rich electorates remain, but not only do the polls put Clinton ahead in both at the moment -- and New York is her current home state -- more importantly, it's highly unlikely that if Sanders were to win he'd do so by the landslide he needs. By and large, with the exception of Sanders's current home state of Vermont and the state right next to it, New Hampshire, his margins of victory haven't been overwhelming, whereas Clinton has racked up several wins in which she mopped the floor with Sanders. He would now have to return the favor over and over again to win the nomination.
The bottom line is this: From this point forward, you can look for Hillary Clinton to move her campaign onto a general election footing. Donald Trump's commanding lead among the Republicans makes him the presumptive nominee and that puts any opponent still fighting an intramural battle at a distinct disadvantage. Clinton obviously still has a campaign to run and Bernie Sanders has both the war chest and the unyielding, quite frankly fanatical support to continue fighting -- even if it's a lost cause -- but she needs to turn as much of her attention as possible to Trump. He's the real threat, both to her presidential aspirations and to the country in general. Trump's rise is frightening; he represents a danger to our democracy that's nothing short of unprecedented and he absolutely cannot be allowed to win the White House. Like it or not, the Democrats are the only thing standing between a narcissistic demagogue worshipped by bigots and the most powerful office in the world and they can't afford to argue amongst themselves or continue to entertain efforts that are assuredly quixotic at this point.
If you're a Sanders supporter, maybe the Democratic electoral system infuriates you. Maybe you think state delegates should be winner-take-all or that the Superdelegate system is somehow a subversion of the will of the people. (It isn't, but maybe you think that.) Regardless, though, the system is what it is. If Bernie Sanders had pulled off the kind of sustained victories Hillary Clinton did there's a good chance he'd be where she is right now, but he didn't. Certainly he had an uphill battle and he's to be commended for how successful he's been in fighting it. Nobody expected him to do as well as he did and it's a testament to the power of his message, particularly with the youth, that he won the number of votes and delegates that he has. He's almost certainly going to go on to win a few more states, maybe even one or two big ones. But barring an honest-to-God miracle, some kind of political deus ex machina, it simply isn't going to be enough. That's the math and it can't be argued or reasoned with.
Tonight almost certainly marked the end for the Bernie Sanders campaign. From here on out he's a dead candidate walking. He can keep fighting and preaching political revolution, and he no doubt will, but in the end there's almost no chance it will win him the nomination. Hillary Clinton has pretty well sewn that up.