During the Democratic presidential primary, many mayors across the country were throwing their support behind former New York mayor Mike Bloomberg, who built relationships with mayors across the country via the training program he sponsors through Harvard. And quite a few mayors of small towns and midsize cities were backing Pete Buttigieg, the young former mayor of South Bend, Ind., who went on to win the Iowa caucuses.

But Atlanta Mayor Keisha Lance Bottoms was always vocal in her support of former vice president Joe Biden — and pretty early in the campaign. Bottoms predicted in a WashPost Live interview that Biden would eventually become the nominee. She told The Post’s Jonathan Capehart:

We know Joe, and Joe knows us. He’s known working people all his life. He’s a blue-collar guy that never forgot where he came from. He knows the importance of a job is more than just wages. It’s about dignity and it’s about respect, and Joe actually understands that.

Bottoms, who will speak at the Democratic National Convention on Thursday night, spoke with me this week about why she was so certain that Biden — who considered Bottoms as a potential vice-presidential pick — would be the one voters chose to go head-to-head with Trump in November.

The answer she gave me referred to a trend that emerged later in the primary contest — that Black women (and particularly older Black women in the South) — were largely behind the candidate who had stood beside President Barack Obama. Bottoms told me:

My best polling source is my mother, and I often think about ‘What does she care about when she goes to her bridge club meeting one a month on Saturday? What are they talking about?’ And with every twist and turn and sometimes stumble through this primary season, she never left Joe Biden. And what was consistent is what I said through the course of the primary and caucus season: ‘We know Joe. And still know where his heart is.’ And I know what he’s doing for this country. And so a lot of times when we’re discussing things on television or on social media, it feels bigger and more off-putting than it actually is. But my test case is my mother or going into the barber shop with my sons. (I ask) ‘what are they talking about in the barber shop? What is my mom talking about in her bridge club meeting?’ And what I saw was that she was not wavering from Joe Biden.

Bottoms endorsed Biden in June 2019 in part because of his experience as vice president leading the country and engaging with global leaders.

“For me, it was most important that we have a president who doesn’t have to walk in the door and figure out where the light switch is, that we have somebody who can lead on Day One,” she told the Associated Press at the time.

The mayor said her confidence that the primary season wasn’t over yet even after Biden failed to win early states came from her reflecting on the 1992 election, when Bill Clinton ultimately ended up winning the nomination despite poor performances in multiple early states.

“I just believe in my heart that was what we were going to see with Joe Biden, and I’m very, very grateful that I was right about it,” she told me.

At the convention, Bottoms will speak about the need for voters who sat out the 2016 election to re-engage with the political process — especially in some of the swing states in the South that could help determine the election.

For the Atlanta mayor whose profile rose this summer after concerns about voter suppression in Georgia captured headlines, this election is not one that left-leaning Americans can afford to skip.

“This has been all about unifying our country,” she told me. “This is about restoring the soul of America, and it obviously is a phrase and slogan we’re using for the campaign, but it’s real.”

“When you look at Donald Trump saying he wants to interfere with our election, that is the most undemocratic thing that you could possibly do and say,” Bottoms added.