After three big wins out west, Democratic presidential hopeful Bernie SandersBernard (Bernie) SandersOvernight Defense: Senate passes 0B defense bill | 3,000 US troops heading to Afghanistan | Two more Navy officials fired over ship collisions Senate passes 0B defense bill Dems fear lasting damage from Clinton-Sanders fight MORE said he thinks many of the party's superdelegates who have pledged to rival Hillary ClintonHillary Diane Rodham ClintonBiden slams Trump over golf gif hitting Clinton Overnight Cybersecurity: Equifax hit by earlier hack | What to know about Kaspersky controversy | Officials review EU-US privacy pact Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain MORE will switch to his side.

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"I think the momentum is with us," Sanders said on CNN's "State of the Union" with Jake Tapper on Sunday. "A lot of these superdelegates may rethink their positions with Secretary Clinton."

The Vermont senator swept Saturday's Democratic contests in Washington, Alaska and Hawaii, easily winning the majority of the 142 pledged delegates in those states. The biggest prize of the day was in Washington, which offered 101 delegates to be split up on a proportional basis.

The latest delegate counts still put Sanders behind Clinton, however, with 975 pledged delegates to her 1,243.

In addition, 469 superdelegates back Clinton, while only 29 support Sanders.

Sanders on Sunday said those superdelegates may begin to see the "reality" that he's the best candidate to beat GOP front runner Donald TrumpDonald John TrumpBiden slams Trump over golf gif hitting Clinton Trump Jr. declines further Secret Service protection: report Report: Mueller warned Manafort to expect an indictment MORE.

"I think when they begin to look at reality, and that is that we are beating Donald Trump by much larger margins than Secretary Clinton," Sanders said. "And then you've got superdelegates in states where we win by 40 or 50 points. I think their own constituents are going to say to them, 'Hey, why don't you support the people of our state and vote for Sanders?'"

This report was updated at 9:31 a.m.