Just two days ahead of the New York primary, Bernie Sanders held one of his biggest rallies ever in Brooklyn's Prospect Park.

Around 25,000 people were at the event on Sunday, the U.S. Secret Service told CBS News. The Sanders campaign said that more than 28,300 people were there, based on the number who went through security screening.

Democratic presidential candidate Bernie Sanders speaks at a rally at Prospect Park in the Brooklyn borough of New York April 17, 2016. REUTERS

"This is a campaign that is on the move. With your help on Tuesday we're going to win right here in New York," Sanders told the crowd, reminding them that he has won eight of the last nine contests.

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The massive rally suggests the grassroots enthusiasm for Sanders' Democratic campaign is alive and well in New York -- the question is whether that will translate into support in Tuesday's primary. The Vermont senator was born in Brooklyn, but New York is Hillary Clinton's to lose. Just about every poll out of the Empire State has shown Clinton with a double-digit lead over Sanders in the state. In the latest CBS News Battleground Tracker out of New York, Clinton leads Sanders, 53 percent to 43 percent.

New York's diverse electorate works in Clinton's favor, as does the fact that the primary is closed to registered Democrats. On top of that, Clinton already has three statewide victories in New York under her belt -- her 2000 and 2006 Senate victories and her 2008 presidential primary victory there.

CBS News' Kylie Atwood contributed to this report.