Despite a 15-point defeat in New York and a slate of challenging primaries next week, Sanders is pressing on and responding to his supporters who remain enthusiastic about his candidacy and are clearly not ready for Clinton.
He drew loud cheers Tuesday from a crowd of more than 6,000 at Penn State University as he ticked through a familiar list of criticism against Clinton, from paid speeches
to Wall Street contributions
. Sanders, whose outsider campaign has featured attacks and anger against the Democratic establishment, drew a hard line against Clinton, and his crowd, at least, reveled in it.
Then, his campaign manager Jeff Weaver defiantly said that even if Clinton went into the Democratic convention with a lead in both pledged delegates and the popular vote, Sanders would pressure the superdelegates to pick him over the former secretary of state.
Clinton's campaign, eager to move past Sanders and focus on the general election, is getting impatient and even angry at some of the attacks.
One in particular has Clinton worried. Sanders' campaign is raising the issue of whether the Clinton campaign is violating campaign finance rules with how it raises money jointly with the Democratic National Committee -- an argument that has the Clinton people "pissed," as one source told CNN.
The concern is that the theme could play into Donald Trump's recent moniker for her -- "Crooked Hillary"
-- especially if he is the Republican nominee.
They worry about the impact of such attacks because they're not aimed just at Clinton but also at the DNC and could weaken the nominee in a general election fight.
Jennifer Palmieri, Clinton's communications director, told reporters Tuesday night that the Sanders campaign "has been destructive" to that point that he is "not productive to Democrats" and is "not productive for the country."
Decrying what she described as "false character attacks," Palmieri compared them to criticism Clinton gets from the GOP. "And any time you mimic Republican attacks, we think that is destructive."
Sanders adviser Tad Devine, speaking on CNN's "At this Hour" Wednesday, rejected calls for a change in tone from the Sanders campaign, citing edit polling from Tuesday.
"I couldn't disagree more with their mischaracterization of what's going on, and I'd point to exit polls from New York," Devine said.
"Now this is in a state where Hillary Clinton won 58% of the vote yet 46% of the New York respondents said the Clinton campaign was more unfair, 34% said the Sanders campaign," he said. "So even in a state that she won overwhelmingly, the voters who had a front row seat to the campaign said they were more unfair."
And 66% of Democrats said the primary contest is "energizing" the party, according to exit polls, Devine noted.
"I hear what they're saying, but what they're saying is being refuted by the voters themselves," he said.
Sanders, speaking to reporters late Tuesday night after arriving home in Vermont, said he plans to return to Pennsylvania on Thursday after taking a day off "to get recharged."
"While I congratulate Secretary Clinton, I must say I am really concerned about the conduct of the voting process
in New York today and I hope that process is changed in the future. I know I am not alone," he said, citing "voter irregularities and chaos at the voting places."
"We think we have a message that is resonating," Sanders added. "We think that the message we are bringing forth that we have got to change a corrupt campaign finance system, deal with a rigged economy, and deal with a broken criminal justice system."
Weaver on superdelegates
But while Sanders was defiant at his rally, it was a television interview with Weaver that got Democrats in both camps buzzing on social media.
Pressed several times by MSNBC's Steve Kornacki about what Sanders would do if Clinton emerged after the June primaries with the lead in both pledged delegates and the popular vote, Weaver eventually declared that the show would go on, with a pitch towards electability in the fall.
"At the end of the day the Democrats are going to have to decide who they want to elect in terms of who's going to be the best in November," Weaver said. "And clearly the polls are almost unanimous now that Bernie Sanders is a much more electable candidate in November
Sanders, Weaver said, would work to win over superdelegates, the collection of more than 700 Democratic party officials and current and former elected leaders free to vote as they please at the national convention.
"They're going to want to win in November," Weaver said, citing Sanders' strong numbers with political independents and younger voters
. "If you can't create a coalition with independent voters, you can't win the White House, you can't win the Senate, you can't bring additional people into the House, so this is what has to be built in November. It has to be Democrats along with independents to defeat the Republicans."
But those superdelegates may also be tired of intra-party fighting by the convention and want to get on with the business of taking on the Republicans, whose front-runner Donald Trump
also had a resounding win in New York on Tuesday.
Devine, meanwhile, said that the Vermont senator will first focus on the next Super Tuesday states.
"We have to do well next week," Devine said Wednesday. "We lost a few more delegates yesterday than I thought we would. We're a little farther behind in the delegates than we'd hoped to be. But I think if we do well next week, then we can get back on course to have a pledged delegate lead by the time voting ends."
And Sanders sent out a fundraising plea Wednesday touting the campaign's hopes for Tuesday.
We still have a path to the nomination, and our plan is to win the pledged delegates in this primary," the email said. "Next week five states vote, and there are A LOT of delegates up for grabs. I am going to keep fighting for every vote, for every delegate, because each is a statement of support for the values we share."
Reconciliation isn't impossible, and general elections have a way of focusing partisan voters. The contest between Clinton and Barack Obama had Democrats wondering if backers of either side could ever support the eventual party nominee. Campaigning in Pennsylvania at this time in 2008, for instance, Clinton said Obama was "too weak" to be president.
"At what point do you say I'm going to keep running but I don't want to damage the nominee's chance?" CNN political analyst David Axelrod, Obama's former campaign manager, said Tuesday night.
"There's an onus on both of them to stick to the issues ... and keep it positive, and start focusing on Donald Trump," Sanders supporter Bill Press said on CNN.
Or, as one Clinton backer told CNN of Sanders: "He has to find a way to land this plane so it doesn't crash and burn the party."