Now that Donald Trump has nailed his manifesto to the door and defined the election in stark and certain terms, Hillary Clinton gets her chance. But unless she suddenly finds a backbone, look for her to deliver a muddled list of Democratic nostrums that satisfies no one.

To compensate for her wishy-washy, flippy-floppy untruthiness, Clinton has loaded her lineup of convention speakers with political sluggers. As such, she seems determined to test the proposition that you can never have too much of a good thing.

But you can, if it means the star of the show gets lost in the crowd and her message looks like a puréed compromise of others’ convictions.

That’s the risk Clinton takes by featuring President Obama and Michelle Obama, Bill Clinton and Joe Biden, Bernie Sanders and Elizabeth Warren. Her husband’s star power is diminishing and the others resemble a reunion of rivals rather than a supporting cast.

It’s weird enough to make you feel sorry for poor Hillary. Well, almost.

She earned her predicament. Having failed to establish a rationale for her campaign beyond a sense of entitlement and inevitability, she is acting like a European-style parliamentary candidate hoping to be selected prime minister by her party instead of an American presidential candidate appealing directly to voters.

Her approach represents a big change from her campaign in 2008, when she exhibited more moxie and certainty. A lurid joke in her race against a young Obama was that she should give him one of her balls so they’d both have two.

Whether it’s circumstance, health issues, or a combination of factors, she’s now running as a shrunken version of that person, quickly trimming her sails to meet the demands of others.

In truth, there was always a taint to her image as a trailblazer because she owes her political career to her husband and especially to his infidelity. After she saved his butt during the Monica Lewinsky impeachment battle, it was no secret he would repay her by helping her win the Senate seat in New York.

Selling pardons to Puerto Rican terrorists and Hasidic thieves in exchange for votes were just some of the unseemly things they did together.

Hillary must finally articulate a rationale for why she should be president and demonstrate that she is leading the party, and not the other way around.

Then, after losing to Obama in 2008, she further compromised her independence by hitching her wagon to his White House. Whatever the truth of their awkward personal relationship, she is now dependent on the president’s support.

She deserved to be indicted in the e-mail scandal, and almost certainly would have been without Obama’s protection. That burdened her with yet another IOU that limits her ability to maneuver around his failed policies.

Suppose, for example, more terror attacks at home force her to take a more muscular approach to the Islamic State. How does she do that without breaking from his refusal even to call the enemy by its name? And what does she say about his limited airstrike campaign, which, as Obama’s CIA head admitted, hasn’t reduced the barbarians’ ability to carry out slaughters in Europe and America?

Obama’s power over her is the black vote. If he signals a lack of enthusiasm for her, turnout among his most loyal supporters could sag and cost her the election. Obviously, Obama doesn’t want to help Trump, but his vanity is easily pricked.

Complicating things even more for Clinton, Bernie Sanders and Elizabeth Warren are also squeezing her. She won the nomination with the backing of the establishment and the connivance of the Democratic National Committee, but Sanders won the hearts of the new generation.

To woo his backers and his endorsement, Clinton repudiated many of her long-held positions. Her stands on trade, criminal justice, Wall Street, health care, college tuitions — all were thrown overboard in a craven bid to save herself.

Some of that is politics as usual, and effective leadership often requires compromise. But Clinton’s reputation for dishonesty is both personal and political, and the nomination crown she has won is battered with dings and dents.

A test will come in her acceptance speech Thursday night. She must finally articulate a rationale for why she should be president and demonstrate that she is leading the party, and not the other way around.

If she succeeds, she’ll be the clear front-runner for November. If she can’t, she will have sold her soul and have nothing to show for it.

Why Blas is really destroying our city

Four headlines from one day: “De Blasio orders less school discipline,” “City Plans Move of Adolescents from Rikers Jail,” “Mayor Unveils Rules on School Detectors” and “Poor Defendants Get Bail Aid.”

All reflect the mayor’s determination to lessen quality-of-life enforcement. His order banning suspensions for kindergarten through second grade is so radical that even the teachers union, an ally, complains it will punish well-behaved kids because troublemakers will be stuck in class.

As for the mayor’s motive, I have a theory: It’s self-interest. Under criminal investigation himself, de Blasio wants a climate of leniency for anyone accused of wrongdoing, just in case.

Brainy like a Fox

Breaking news alert: A slew of major media organizations all used the same word to describe Donald Trump’s convention speech: “dark.”

The New York Times, Washington Post, CBS, NBC and ABC all somehow reached the exact same conclusion. The New Yorker magazine doubled down and called the speech “dark, dark.”

Such media groupthink is why Roger Ailes created Fox News 20 years ago. He believed America was ready for a news organization that didn’t share a single, liberal brain with all the others.

Even he was surprised at how ready the nation was for something different. I joked with him once that he found a niche audience — half the country. That was true, and sometimes an understatement, with Fox often drawing more viewers than all its competitors combined.

Ailes stepped down last week after being sued for sexual harassment by former anchor Gretchen Carlson. Reports say other women told corporate investigators they, too, felt uncomfortable with things Ailes said or did.

Although I am a Fox contributor, I know nothing other than what I read about the allegations, which Ailes denies.

What I do know is that Roger Ailes is a genius who mastered both politics and television and hitched them together to create a cultural force that is here to stay.

He is also a generous and complicated soul who took chances on young journalists and gave older ones a second chance. Personally, I remain grateful to him and wish him a very long and happy life.

Eaten by pay hike

The quote of the week comes from Larry Georgeton, who is closing the Del Rio Diner in Gravesend, Brooklyn, after four decades because of the coming $15 minimum-wage law.

“We’d need to raise the burger to $9 from $6.45,” he told The Post. “I don’t want to do that to my customers. They’ve been good to me. These are middle-class people.”