New York City Mayor Bill de Blasio spent Sunday urging voters to head to the polls on Tuesday, as Sal Albanese, his leading rival in the Democratic primary, pushed back against a widely held belief that the incumbent was a shoo-in to win.

“I’m very concerned about turnout levels,” de Blasio said in an interview with WABC radio host Rita Cosby. “ . . . just because I don’t believe it’s healthy for our democracy.”

De Blasio, who has outspent and outpolled Albanese, a former city councilman, greeted voters in the East Village and East Harlem, addressed churchgoers in Harlem, and rallied supporters at a barbecue in the Bronx.

Albanese, who has raised some $200,000 in campaign contributions compared to the $4.9 million amassed by de Blasio, capped off a day of meeting prospective voters in the Upper West Side, Upper East Side and Greenwich Village, by accepting the endorsement of the 318 Restaurant Workers Union at a Chinatown news conference.

De Blasio, speaking to congregants at the First Corinthian Baptist Church, said he “humbly” sought their support on Tuesday to build on his first-term record. He touted his push to bring free Pre-K for all city four-year-olds, saying he hoped to extend the program to all city three-year-olds during his second term.

“We need to make a lot more change,” de Blasio said. “It’s your city, but so much more has to change so it can keep getting better and better for you. So it can be affordable for you. So it can work for your children. So it can be safe for you. so it can be fairer.”

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Albanese, flanked by members of the restaurant union that represents about 159 workers, acknowledged in a speech to supporters the uphill climb to defeat de Blasio but said he was running in part to keep the influence of deep pocketed donors out of politics.

“We can do this, but it’s not going to be easy,” Albanese said, later adding “we are the people . . . they don’t have the majority, they just have the money.”