Democratic presidential hopeful Bernie Sanders Bernie SandersKenosha will be a good bellwether in 2020 Biden's fiscal program: What is the likely market impact? McConnell accuses Democrats of sowing division by 'downplaying progress' on election security MORE's wave of momentum is growing, with another state win Tuesday in Wisconsin, his seventh victory of the past eight contests.

The results of Democrats voting abroad were announced on March 21. Then on March 22, Sanders won in Idaho and Utah, but not in Arizona. Four days later, he swept caucuses in Alaska, Hawaii and Washington.

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The Vermont senator has been touting his success, claiming that he is beginning to convince Democratic superdelegates to support him instead of former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE.

"I think the momentum is with us," Sanders said the day after his caucus sweep. "A lot of these superdelegates may rethink their positions with Secretary Clinton."

March also saw the Sanders campaign set a new fundraising record, with the $44 million for the month, largely in small online donations.

But even with his momentum and financial resources, Sanders is still facing an uphill battle in the delegate race.

Sanders entered Tuesday trailing Clinton by 263 pledged delegates, according to The Associated Press. But because Democrats award their delegates proportionally, he would need to start winning states by large margins in order to catch up.

And even if he manages that, his chances may rest on winning over superdelegates, the majority of whom have backed Clinton. She has won over 469 superdelegates so far, while Sanders only has 31.