After three big wins out west, Democratic presidential hopeful Bernie SandersBernie SandersSanders: FBI inquiry of wife is 'pathetic' attack Why UK millennials voting for socialism could happen here, too WATCH LIVE: Senate Dems hold ‘People’s Filibuster’ against ObamaCare repeal MORE said he thinks many of the party's superdelegates who have pledged to rival Hillary ClintonHillary Rodham ClintonPro-Trump group pulls ads targeting GOP senator on ObamaCare repeal Stone to testify before House Intel Committee next month Overnight Cybersecurity: New ransomware attack spreads globally | US pharma giant hit | House intel panel interviews Podesta | US, Kenya deepen cyber partnership 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 TrumpScarborough defends CNN against Trump: CNN 'has more integrity' Time asks Trump Organization to remove fake cover from golf clubs Why UK millennials voting for socialism could happen here, too 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.