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Indeed, the Vermont senator would need to win 65 percent of the remaining pledged delegates in order to take the lead over Hillary Clinton in pledged delegates, according to an ABC News analysis of the delegate count.
By contrast, Clinton needs 35 percent to keep her lead.
"What our polling suggests is it is going to be a very steep climb," Sanders said Sunday night on the campaign trail, referring to the 65 percent he would need.
From there, Sanders would need to persuade superdelegates who’re overwhelmingly in Clinton’s camp to switch to his side. But it’s still likely that Sanders will block Clinton from clinching the nomination using pledged delegates.
She needs to win an average of 68 percent of the vote in remaining states in order to lock up the 2,383 magic number without help from superdelegates.
Sanders has repeatedly talked about how the superdelegate system is "rigged," but new tabulations suggest that even if superdelegates voted along the same lines as the people in their state, that would not give Sanders the edge.
"When we talk about a rigged system, it’s also important to understand how the Democratic Convention works,” Sanders said at a rally today in Evansville, Indiana. “We have won, at this point, 45 percent of pledged delegates, but we have only earned 7 percent of superdelegates.
“So, in other words, the way the system works, is you have establishment candidates who win virtually all of the superdelegates. It makes it hard for insurgent candidacies like ours to win.”
That said, if all the superdelegates in states that have already voted aligned with the general Democratic populations of their respective states, Clinton would have 374 superdelegates and Sanders would have 147, the ABC News analysis shows.
That split is certainly less wide than it is now -- Clinton has 520 super delegates while Sanders only has 39 – but it still wouldn’t give Sanders enough to take the lead.
And barring a catastrophe for Clinton in Indiana, there will be no way for Sanders to earn enough pledged delegates to secure the nomination outright after Tuesday. He would have to rely on superdelegates.
Sanders did pick up a handful of superdelegates who were previously uncommitted in Vermont, Utah and Nevada, according to his campaign sources.
In spite of that, Clinton is squarely in the lead when looking at the total number of delegates.
Of Indiana's Democratic delegates, 83 are allocated proportionally and there are nine others that are superdelegates, who can wait until the summer convention in Philadelphia to pledge their support to a candidate.
"Bernie will still pick up some [delegates] so he won't be completely blocked out, but momentum is working against him," said David Campbell, chairman of the political science department at the University of Notre Dame in Indiana.
"The more and more that Hillary does appear to be the inevitable nominee, the harder it will be for Bernie," Campbell told ABC News.
"His die-hard supporters are going to show up and support him regardless."
ABC News' MaryAlice Parks contributed to this story.