In a series of television interviews, Sanders remained defiant despite what he acknowledged was an uphill fight to overtake front-runner Clinton.
Mr Sanders also backed a challenger to the Democratic National Committee's chairwoman.
Clinton has said she already considers herself the de facto nominee and is increasingly turning her attention to Donald Trump, saying on Sunday that the rhetoric of the presumptive Republican nominee was dangerous.
Sanders told ABC's "This Week" program that Americans should not have to choose between "the lesser of two evils" in the Nov. 8 election.
Sanders said that if he won the White House, he would not reappoint US Representative Debbie Wasserman Schultz as DNC chairwoman.
He also endorsed law professor Tim Canova, who is challenging the Florida congresswoman in the August Democratic primary.
"Do I think she is the kind of chair that the Democratic Party needs? No, I don't," Sanders told CBS' "Face the Nation."
"Frankly, what the Democratic Party is about is running around to rich people's homes and raising obscene sums of money from wealthy people. What we need to do is to say to working-class people – we are on your side," he said.
The defiant tone by Sanders, a US senator from Vermont, has worried some Democrats anxious to see Clinton begin to unify the party and turn her attention to an election showdown with Trump.
Clinton painted Trump as a risk of the sort voters had not seen before in an interview with NBC's "Meet the Press" that aired on Sunday.
"I do not want Americans, and, you know, good-thinking Republicans, as well as Democrats and independents, to start to believe that this is a normal candidacy," she said. "It isn't."
Trump has gained ground in opinion polls as Republicans begin to rally around his candidacy. A Washington Post-ABC News poll released on Sunday showed Trump with a 2-point lead over Clinton, within the margin of error. In early March, Clinton led Trump by 9 points in the same poll.
But Sanders has ignored growing Democratic calls to step aside and repeated his vow to stay in the race until the party's July 25-28 nominating convention in Philadelphia despite Clinton's nearly insurmountable lead in pledged convention delegates who will choose the nominee.
He said he wanted to do away with superdelegates - party leaders who are free to support any candidate. Their rush to back Clinton even before votes had been cast amounted to "an anointment process," Sanders said.
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