Singer Madonna, right, and her son David Banda perform in support of Democratic presidential candidate Hillary Clinton at Washington Square Park on Monday in New York.

NEW YORK — Madonna belted out some of her biggest hits on Monday night as she treated people in the city to a surprise outdoor concert in support of Democratic presidential nominee Hillary Clinton.

About 300 people jammed into Washington Square Park, in the heart of Manhattan, to watch the pop singer perform “Express Yourself,” “Don’t Tell Me,” “Imagine,” “Like a Prayer” and “If I Had a Hammer” while they sang along.

Madonna opened the 30-minute performance by urging the crowd to vote on Tuesday.

“This is a concert that is about unifying us, and it’s about keeping America great, not making America great again,” Madonna said. “Tomorrow we’re going to keep America great. We’re going to elect a president that does not discriminate.”

As she finished the concert, she again urged the growing crowd to go to the polls and vote for Clinton.

“New York! Tomorrow is the big day. Are you listening?” She said. “Do we want Donald Trump to be president?”

“No!” the crowd roared back.

“Do we need Hillary Clinton?”

“Yes!”