The Democratic nominee must win 2,383 delegates to secure the nomination, but with only 933 delegates up for grabs in the remaining contests, it is impossible for Sanders to get there just by winning contests against front-runner Hillary Clinton. The Vermont senator has racked up 1,444 delegates, according to the latest CNN delegate tally, but would need to win more than 100% of the remaining delegates.
Asked about this hurdle Wednesday, Sanders campaign manager Jeff Weaver dismissed it.
"The truth is, no one is going to the convention with the requisite number of pledged delegates to win. The superdelegates are going to decide this race," Weaver said on CNN's "New Day."
The comment wasn't as much a guarantee as a promise from the Sanders camp that they would fight Clinton all the way to Philadelphia with the hopes of putting her in the same boat as them, fighting over superdelegates.
Sanders could still collect enough delegates to deny Clinton the nomination before Philadelphia.
Clinton is just 165 delegates shy of the nomination on the surface, but that tally includes superdelegates, who are not locked in until they cast their vote in July. Not including Democratic superdelegates, she is 678 delegates shy of the nomination.
The Sanders campaign promises it has been running an aggressive campaign to peel superdelegates from her, but it appears to have paid little dividend.
For the past month, the focus of a convention battle has been squarely on the Republicans, as Ted Cruz appeared close to forcing Donald Trump into a behind-the-scenes delegate battle. But that evaporated when Cruz dropped his bid after a grueling loss in Indiana.
A Sanders aide immediately latched on to the irony Tuesday night.
"So who's going to have a contested convention now?" said the adviser, who spoke on the condition on anonymity, just as Cruz announced he would no longer pursue the GOP presidential nomination.
As Cruz's fortunes soured Tuesday night, the Sanders campaign appeared to gain new energy with a surprise win over Clinton in Indiana. His win came after a series of grueling losses in the Northeast and the layoff of more than 200 staffers.
And after shocking many by beating Clinton in the fundraising race for the first three months of the year, the Sanders campaign reported a more modest $26-million haul in April, $10 million less than Clinton pulled in last month.
While Trump was fighting against Republican system he said was "was "rigged" and "corrupt," he also saw an opportunity to goad the Democrats.
"Bernie Sanders has been treated terribly by the Democrats—both with delegates & otherwise. He should show them, and run as an Independent!" Trump tweeted on April 26, instigating a move that would clearly siphon support from Clinton in a general election but appears highly unlikely.