Hillary Clinton’s campaign for president was tested by several emphatic defeats on Saturday at the hands of Bernie Sanders, who continued his quest a day later to reinvigorate his campaign and challenge her on her home turf: New York.

In Washington, Alaska and Hawaii, Sanders won by margins of about 42 points or more – even larger than Barack Obama’s victories in 2008 – and raised the question of whether the senator from Vermont could win upsets in the coming contests in Wisconsin and New York.

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On Sunday, Sanders claimed that his western wins opened a clear “path to victory” for the Democratic nomination, but though he gained 45 pledged delegates, Clinton still has more than 250 more bound delegates than the senator. Sanders also faces a deficit of 440 “superdelegates”, party officials who can vote in the convention but are not bound to follow their states’ results.

Sanders told CNN that his campaign could surmount the gap in pledged delegates. “I think every vote is pivotal. We are now winning state after state with the Latino vote,” he said. “We’re doing extraordinarily well with young people, and we do think we have a path toward victory.”

Related: After a night of sweeping victories, Bernie’s back | Lucia Graves

But the senator’s victories on Saturday came through states where he held distinct advantages. White voters, like those who dominate Washington and Alaska, tend to favor Sanders, and all three states on Saturday staged caucuses, whose open doors and freewheeling organization tends also to play to Sanders’ strengths with independent voters.

The election schedule ahead has few similar states. After Wisconsin, a round of large, north-eastern states with diverse electorates will vote, and in closed primaries that only allow registered party voters into the polls. Sanders’ silver lining, which he noted repeatedly on Sunday, is that he is unlikely to be as battered as he was in the southern states where Clinton found overwhelming support from black voters.

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Sanders even predicted the primary season would ease for him, and cast his eye toward California, the last state to hold elections.

It’s not clear whether Sanders, despite the record small donations to his campaign, can last as long as early June, and he badly needs a win Wisconsin on 5 April to maintain any of the “momentum” he boasted of Sunday.

So far, midwestern states have split between the candidates: Clinton narrowly won Illinois, and Sanders sneaked victories out of Michigan and Minnesota. Wisconsin is more white than Illinois , but economically may have more in common with states that have broken for Clinton.

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Because of Clinton’s overall lead of 708 pledged and unbound delegates , pressure is on for Sanders to win big – or at least do surprisingly well – in Pennsylvania and New York, where 210 and 291 delegates respectively will be at stake. On 26 April, four other eastern states will poll alongside Pennsylvania, offering 253 delegates between them.

Acknowledging Clinton’s superdelegate advantage, Sanders hinted at a campaign to convince the free agents to defect to his cause. He argued that the officials should listen to their constituents, and that he, not Clinton, has the best chance to beat the Republican frontrunner, Donald Trump, in November.

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“A lot of these superdelegates may he rethinking their decision, a lot of them have not declared,” he said. “I think their own constituents are going to say to them, ‘Why don’t you support the decision of our state and support Senator Sanders?”’

While the Clinton campaign had predicted strong performances for Sanders over the weekend, her campaign manager, Robby Mook, has said it is impossible for Sanders to catch up. Still, New York represents a clear target for Sanders – born and raised in Brooklyn – to cut into her lead and embarrass Clinton in the state she represented as senator.

Sanders’ path through the Empire State has many obstacles, however, including New York City’s 50% nonwhite population and Sanders’ adamance that Wall Street power brokers bear much of the fault for inequality and corruption around the US.

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The senator showed no sign that he would cease his attacks against financiers in the hopes that Manhattan Democrats might vote for him over Clinton. He called the “big money” rallying for Clinton “obscene”, and pointed to a fundraising dinner hosted by the actor George Clooney, where supporters were invited to pay as much as $353,000 per ticket.

“It is obscene that Secretary Clinton keeps going to big money people to fund her campaign, and it’s not just this Clooney event,” Sanders told CNN. He said Clinton also relies on Wall Street and corporate donors, as well as political action committees known as Super Pacs.

“I have a lot of respect for George Clooney. He’s a great actor, I like him”, Sanders said. The problem, he said, was not Clooney “but [that] the people who are coming to this event have undue influence over the political process”.

At the same time, Clinton’s aides and allies have quieted their once vociferous attacks on Sanders, and the candidate herself did not take part in the campaign ritual of trying to reach voters with television appearances. The staffers and surrogates have made clear that they believe her nomination inevitable, and now fear that attacks will make it harder to unify Sanders’ supporters under Clinton’s banner against a Republican candidate.

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Related: Call him Birdie Sanders: bird interrupts Oregon rally to thunderous applause

Two Clinton allies, for instance, senators Chuck Schumer and Barbara Mikulski, recently dissuaded several other pro-Clinton senators from calling on Sanders to abandon his campaign, according to the Washington Post . Sanders has said such calls are “outrageously undemocratic”.

But the effort to win over Sanders’ supporters must overcome deep distrust. In Washington on Saturday, some independent voters said they would rather vote for a third party candidate than Clinton in a general election. And when long queues formed at polling stations in Arizona last week, Sanders voiced suspicion that the situation had been created by Democratic party officials.

A Clinton lawyer even took to a pro-Sanders forum to shield his candidate from blame, and to direct it toward Republicans.

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“What happened in Arizona is bad for both Senator Sanders and Secretary Clinton,” wrote campaign counsel Marc Elias. He added that Clinton had a plan to address the problem ahead of the November vote – “but I’m really not here to plug my boss!”

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