The strongest indicator yet that Hillary’s mulling a 2020 run? She appeared Wednesday, for the first time ever, on Howard Stern.

There was hardly a pretense she was there to promote the book she co-wrote with daughter Chelsea, long ago a bestseller.

As those who listen to the show know, Stern publicly begged Hillary to appear during the 2016 campaign. After Donald Trump won, Stern said one guest shot could have moved the needle her way.

“If she had come on the show …,” Stern mused in May. “The way I helped Donald was I let him come on and be a personality. Whether you liked him or not … people related to him as a human being.”

Hillary, it’s clear, was after exactly that — relatability, long her white whale.

One can only ask: Why now, if she has no plans to run yet again?

Sure, it’s possible she just loves being part of the national conversation. But of all the venues such a serious stateswoman could choose, one whose public presentation has been so carefully cultivated over decades, really: Howard Stern?

She hasn’t closed the door on 2020. Just this past weekend, during an appearance on the UK’s “Graham Norton Show,” Hillary said she’d been “deluged” with pleas to run again.

“I’d have to make up my mind really quickly,” she said, “because it’s moving very fast.”

A reference, perhaps, to latecomer Mike Bloomberg?

Stern was an able ally, allowing Hillary to expound on her ability to work across the aisle (despite no signature legislation while serving New York in the US Senate), her support for the Osama bin Laden raid and her role in advising the president, her plans for her first 100 days as president (health care), and her concerns for the future of the country, which felt especially raw during Trump’s inauguration.

“If I had lost to a normal Republican,” Hillary said, “I wouldn’t have a pit in my stomach.”

Given this was Stern — truly one of our best interviewers — we got some gems.

“Contrary to what you may hear, I actually like men,” Hillary said, leading Stern to flat-out ask, “You’ve never had a lesbian affair?”

Amazing. George Stephanopoulos, Chuck Todd, Norah O’Donnell, et al., take notes!

Hillary, laughing, again said no, and went on to discuss everything from her mother’s depression to whether she’s ever been in therapy (no, but marriage counseling post-Lewinsky), to her stiffness in the spotlight (“It’s outside my comfort zone”), to the true charisma that she lacks but that her husband and Barack Obama, she readily admits, have in spades, to her friendship with Mick Jagger (!) and how the deaths of her younger brother and two close friends this year have devastated her.

Even a coughing fit, which became a campaign meme about her ostensibly dire health, didn’t faze Hillary.

“I thought I’d come on and cough some more,” she joked.

Never has Hillary Clinton sounded this relaxed, conversational and, yes, human. She sounded like anyone you may know. None of Howard’s verbiage — “Do you ever just lay in bed and say, ‘F–k this, I’m getting out’?” — left her flummoxed.

Hillary proved she could hang.

Howard’s listeners agreed, flooding the airwaves after she left.

“She moved me to tears,” said one female listener. “If she had only come on when she was running, she would have won.”

“I did, three years ago, vote for Trump, but if she had come on during the election, my vote would have swung 150 percent.”

“I’m a conservative. I’ve always hated Hillary. This interview changed my [mind] … I had no idea how cool she was.”

“I wanted to tell her I’m sorry we believed the hype and we did not elect a presidential person. I wish we would have known this Hillary three years ago.”

“I just finally saw the human side of Hillary. She’s stellar.”

“Listening to her now … I think she should run again.”

For the past three years, Hillary has infamously blamed Russian interference, misogyny, Bernie bros, WikiLeaks, the Comey memo, low-information voters, voter suppression, the Electoral College, etc. for her loss. But on Stern, she added a telling regret.

“I think you were right,” she said of his repeated requests that she appear on his show in 2016. “I did not prioritize the media the way I should have. I think that was a miscalculation. I really do.”

And whom, Howard asked, will she be supporting in 2020?

“Whoever can win,” she said.

It sounds like she thinks that’s her.