Leading Democrats privately predict that Hillary Clinton will win a closer-than-originally-expected victory over Bernie Sanders in the April 19 primary — but they’re also conceding that “Clinton exhaustion” could produce a surprise upset.

“The feeling is that Hillary is kind of like Spencer Tracy running one last race in ‘The Last Hurrah.’ It’s like, ‘Here we go again,’ the same Hillary and Bill show that’s been going on for 24 years,’’ a top state Democrat who knows the Clintons well told The Post over the weekend.

“There’s a shelf life, nobody lasts forever, and add to that that Hillary seems shrill at times and is groveling in changing some of her positions to the left in order to head off Sanders, and you can see why people feel the way they do,’’ he continued.

The source said that while most Democratic officials “think Hillary is going to win’’ a tight victory, he also cautioned that “We all talk to each other, and it’s very possible that if there’s a wave coming for Bernie that we don’t see it and it could sweep Hillary away.’’

Other Democrats echoed the source’s statements, with one saying, “Everyone is being mobilized, everybody is working hard for Hillary, but everybody is kind of up there in age and there’s a sense of ‘Clinton exhaustion,’ plus we keep seeing all these young people out there working for Bernie.’’

All the state’s leading Democrats have endorsed Clinton — but Gov. Andrew Cuomo, as the de facto head of the state party, has the most riding on the outcome, party insiders agree.

“Andrew is in a funny spot: He’s the leader of the party, and as such he’s got to at least look like he’s doing everything to help Hillary — yet his own ambition [to run for president] leads everyone to think he’d like to see her lose,’’ said a Democratic operative who knows Cuomo well.

“If Sanders was to win, or even come close to Hillary, that will be a hell of a black eye for Cuomo and New York Democrats generally, and it would leave people wondering if maybe the governor could have done more to help,’’ the operative continued.

Cuomo may actually be a hindrance to Clinton, who found herself unexpectedly booed at a New York State United Teachers gathering Friday when she praised the governor, who has tense relations with the state’s teachers unions.

Influential backers of Ohio Gov. John Kasich’s New York efforts say he’s making a tactical error by spending too much time upstate and not enough time in the city and the suburbs.

“Upstate, with few exceptions, is really Trump and Cruz territory, but Kasich really would have a shot at picking up 10 to 15 delegates in the congressional districts in the city and the suburbs, so I don’t know what he’s doing,’’ said a prominent Republican activist who would like to see Kasich out-poll both Donald Trump and Ted Cruz.