The delegate math looks daunting for Sanders, especially after his 14-point loss to Hillary Clinton in New York
, but his advisers insist he still has a legitimate path to victory.
"The conversation is what it always is: It's how we advance the senator's agenda in this country, how we move toward the nomination," Sanders' campaign manager Jeff Weaver told CNN's Chris Cuomo on "New Day." "The senator certainly has a path to victory in this contest, and we're going to do everything we can to make that happen."
While Weaver made the case that Sanders will cut into Clinton's pledged delegate lead in the upcoming contests, he also sought to undercut Clinton's advantage by stating her lead relies mostly on superdelegates -- unbound party officials and elders.
"If you just look at pledged delegates, the secretary only has a 250- to 240-delegate lead. That's less than half of the number of delegates that are going to be assigned in California alone," Weaver said.
But many analysts point out that because Democrats award delegates on a proportional basis, Sanders is running out of states -- and time -- to catch Clinton.
The Sanders camp has said it will begin wooing the superdelegates to his side.
Karen Finney, a Clinton spokeswoman, called Sanders' plan to flip superdelegates "unprecedented and undemocratic."
"They're talking about trying to win by overturning the will of the people. That is antithetical to everything Sen. Sanders says he is about," Finney said on "New Day."
Sanders' wife Jane told CNN her husband's candidacy is actually improving the democratic process.
"We are doing everything we can to bring people into the Democratic party, and at the primaries, the door is being shut on them," she said.
Sanders would need to win 82% of the delegates in the remaining primary races, including superdelegates, while Clinton only needs 32%, according to CNN calculations.
"Next Tuesday, there are five states in play, there's one week in May ... June 7, a huge day, California, New Jersey. There's a long way to go in the process," Weaver said.
'Will of the voters'
But some of Sanders' supporters may balk at his effort to secure the nomination by flipping superdelegates while trailing Clinton in the pledged delegate count and popular vote.
The progressive group MoveOn.org, which endorsed the Vermont senator, launched a petition stating
, "The race for the Democratic Party nomination should be decided by who gets the most votes, and not who has the most support from party insiders."
"That's why we're calling on all the Democratic superdelegates to pledge to back the will of the voters at the Democratic Party convention in Philadelphia," it says.
Ben Wikler, Washington director of MoveOn.org, told the Huffington Post
that more than 380,000 MoveOn.org members have signed petitions in support.
"MoveOn members overwhelmingly endorsed Sanders for president, and we want him to win the most pledged delegates, become the nominee and become president," he said.
The Sanders camp continues to argue it's the best hope for Democrats in the fall.
"If you look at the exit polls out of New York, when they asked people who had the most unfair campaign, by double digits, even though Secretary Clinton won the popular vote, the people of New York said the secretary was running a more unfair campaign," Weaver said.
But Clinton, as evidenced by her victory speech on Tuesday, is ready to move on to the general election -- while remaining sensitive to Sanders and his supporters.
"We started this race not far from here on Roosevelt Island. And tonight, a little less than a year later, the race for the Democratic nomination is in the homestretch and victory is in sight," Clinton said to a crowd in Manhattan on Tuesday shortly after her primary victory. "To all the people who supported Sen. Sanders, I believe there is much more that unites us than divides us."
However, Sanders' fundraising prowess -- regardless of his place in the polls, delegate count or popular vote -- means he's largely in the race for as long as he wants to be. He raised $44.7 million in contributions in March, according to the most recent federal filings. Clinton raised $26.3 million.
"We're honored to have the strong support of 2.2 million passionate donors who have given more than 7 million times," Weaver said in a statement
. "It's because of them that our campaign can take on the establishment and win eight of the last 10 primaries and caucuses."
Overall, the Sanders campaign has raised $182.9 million, compared to $182.2 million for Clinton.