ABC News April 27, 2016

How Bernie Sanders' Strategy Will Evolve Going Forward

WATCH: Hillary Clinton Vows to 'Unify Our Party'

Bernie Sanders stood unwavering and a little audacious at his first rally in Indiana today.

Despite losing an additional four states on the east coast the night before, which rendered his chances of winning the nomination nearly mathematically impossible, the senator said he believed he would still win the majority of the pledged delegates and was staying in the race to win it.

“So that there is no confusion, we are in this campaign to win and become the Democratic nominee,” he said speaking to a packed room at Purdue University. In a statement released overnight after the final results landed, Sanders notably did not say whether he still believed he could make up Hillary Clinton's lead in pledged delegates, which some interpreted as a near concession on his part.

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After Clinton’s latest victories, Sanders would need to win each of the remaining states by 35 points, or 65 percent of the remaining pledged delegates to take the lead on that front. Considering the number of superdelegates who have already pledged their support to Clinton, the former Secretary of State now would only need to win 20 percent of the remaining delegates to reach the threshold for the nomination.

Sanders briefly acknowledged that he was losing the race, but essentially posited that he was hoping for a miracle.

“I am very good in arithmetic and I can count delegates and we are behind today but you know what? Unusual things happen in politics,” he continued at his rally. "And with your help we are going to win the pledged delegates."

Sanders' Strategy Moving Forward

A major part of Sanders’ strategy now seems to be appealing to those superdelegates as well, who do not technically vote until the convention and will likely be the ones to officially put either candidate over the edge. There has been little evidence so far that many party elites are considering switching their allegiances at this late stage. Still, the senator made his pitch today, citing the excitement around his campaign, the large crowds he draws, and how well he does with independents as reasons he is better positioned to represent the Democratic Party.

Sanders added that even if he did not win, his team would fight through the end and try to win to as many delegates as possible in order to put pressure on the party and Clinton.

“We intend to win every delegate that we can so that we when we go to Philadelphia in July we will have the votes to put together the strongest progressive agenda that any political party has ever seen,” he said. In his statement late Tuesday, Sanders specifically listed a $15 dollar minimum wage, the end of hydraulic fracking and universal health care as key components of that platform.

One of the senator's grassroots backers, Democracy for America, echoed Sanders’ firm stance that the onus was on Clinton to unite the party under a more progressive agenda, saying in a statement that the question was “whether the Democratic establishment [was] going to bring our party together by embracing our fight for a political revolution or tell us to sit down, shut up and fall in line.”

So far, Clinton and her campaign have reminded voters and the press that in 2008 she unconditionally backed her opponent Barack Obama once the nomination was out of her grasp and they have urged Sanders to do the same. On the one hand, Clinton will likely not need Sanders’ delegates to put her over the threshold for the nomination -- a fact limiting his negotiating power at the convention and before -- but she will want voters from his wing of the party to remain engaged going into the fall.

Another factor potentially impacting Sanders’ plan to persevere: Donald Trump. The billionaire said today on MSNBC that he was planning on “taking a lot of things Bernie said and using them” in his own campaign against Clinton. Sanders has said repeatedly that his priority will be make sure a Republican does not win in November. Should Trump in fact start quoting him, the pressure from all sides could make him change how he talks about Clinton. Last night and today, Sanders’ notably did not mention Clinton's paid speeches to Wall Street firms, one of the subjects on which he has been particularly aggressive.

A Concession of Ideas, Not Just Delegates

Sanders’ most ardent fans have not been surprised by their leader’s defiance. After all, the senator has been arguing all along that the country’s entire political system is fundamentally broken and platforms of the Democratic Party are too narrow. He has spoken since the beginning of building a movement, not just electing a candidate. To back Clinton now could look like a concession of ideas, not just delegates.

“It's not just about Bernie, It's about the mindset that Bernie has. He’s all about for the people not individual,” Mary Crow, 20, a student and Sanders’ fan said Tuesday night in at Sanders’ rally in Huntington, West Virginia. She had made matching shirts with her friend, Rapen Hall, that read “#BernieorBust #NeverHillary #NeverTrump.”

“I firmly believe that there will be people just like him in the future. I don't think it's over. Even if he doesn't win, it’s just beginning,” Hall continued. “I can't believe how many people turned up today.”

For Sanders, a political revolution means in large part more active civil engagement, and Sanders reiterated today that whether he is elected or not he wants to see voter turnout increase substantially across the country. By continuing his speaking tour and delivering addresses mostly on college campuses, Sanders can in theory continue to gin up support and enthusiasm around his issues, though it remains to be seen where or how he will ask his fans to specifically direct their efforts should his campaign officially end.

Sanders has just begun using his email list and fundraising machine to back local candidates whose agendas align with his. In last few weeks, he has sent fundraising emails in support of three congressional candidates in Nevada, Washington State and New York, perhaps a sign that more of this will come as well.

ABC News' Ryan Struyk contributed to this report.