Democratic presidential candidate Bernie Sanders cranked up his fight with party leaders on Sunday, backing a challenger to the Democratic National Committee's chairwoman and accusing the party's establishment of trying to anoint Hillary Clinton as the nominee for president.

In a series of television interviews, Sanders remained defiant despite what he acknowledged was an uphill fight to overtake front-runner Clinton.

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.

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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 U.S. 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 U.S. 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.

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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.

He promised to influence the party platform and party rules even if he was not the nominee, but said if Clinton did not move toward his views on reining in Wall Street, reducing income equality and other issues, "she's going to have her problems."

"I don't want to see the American people voting for the lesser of two evils. I want the American people to be voting for a vision of economic justice, of social justice, of environmental justice, of racial justice," he said on ABC.

After Sanders' endorsement of her opponent, Wasserman Schultz said in a statement that she would remain neutral in the Democratic presidential race.

Democratic worries about party unity were exacerbated by last weekend's state party convention in Nevada, where unhappy Sanders supporters disrupted the proceedings in a dispute over rules.

That raised fears about possible chaos at the national convention in Philadelphia. But Sanders disputed media reports describing the Nevada incident as violent.

"What happened is people were rude, that's not good, they were booing, that's not good, they behaved in some ways that were a little bit boorish, not good, but let's not talk about that as violence," he said on ABC.

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Sanders said he was not encouraging protests at the Philadelphia convention, "but of course people have the right to peacefully assemble and make their views heard."

Clinton said in the NBC interview that she would talk to Sanders about his policy demands and take them into account "when he's ready to talk."