She danced the merengue in Washington Heights. She slammed down a mean game of dominoes in East Harlem.

And in the East Village the day before the New York primary, Hillary Clinton broke her long-held rule of not eating in front of the news media by digging into an ice cream concoction named the Victory.

Mrs. Clinton seemed, for the first time in a rocky and unpredictable Democratic race, relaxed. “That’s what’s so great about being back here now for this primary,” she said at Mikey Likes It Ice Cream, where the owner had named the dessert in her honor. “I get to go to a lot of the places that I love. I get to meet new people and see people I’ve known for a long time.”

Mrs. Clinton has had dramatic highs and crushing lows in her political career and in this campaign. But since she first ran for office 16 years ago, New York has always been the state that loved her back, and on Tuesday it delivered one of her biggest boosts yet toward becoming the first woman to capture the Democratic Party’s nomination for president.