Forty-two years ago, Lita Rosario-Richardson was the only woman on Howard University's debate team. She made sure that changed -- successfully recruiting Kamala Harris.

"I noticed Kamala's analytical skills and critical thinking skills and that she had a very cogent way of making arguments," said Rosario-Richarson.

Rosario-Richardson and Harris' former debate opponents are some of the people who know her debating style best. Many of them are now expressing for the first time how Harris' earlier debates could impact her upcoming one on Sept. 10 against former President Donald Trump.

The ABC News presidential debate will take place on Sept. 10 at 9 p.m. ET and air on ABC and stream on ABC News Live, Disney+ and Hulu.

Seizing a moment

When then-San Francisco District Attorney Kamala Harris took the stage against Los Angeles District Attorney Steve Cooley in the general race for California attorney general in 2010, Harris was trailing in the polls.

A reporter asked Cooley about accepting both his pension as a former LA district attorney and an attorney general salary, which would bring him over $400,000 from taxpayers.

"I definitely earned whatever pension rights I have and I will certainly rely upon that to supplement the very low - incredibly low salary that's paid to the attorney general," Cooley responded.

Harris' campaign turned Cooley's answer into a campaign ad.

Her former aides tell ABC News that Harris had hoped to focus the race on her accomplishments and vision, but she signed off on the ad regardless.

In an interview with ABC News, Cooley said "I think she had very good consultants who constructed an ad," but added he thought Harris "was not smart."

On election night, Cooley was narrowly ahead and initially claimed victory, but Harris emerged as the winner when the votes were fully counted weeks later.

Cooley said he had not watched the debate since it happened, but he predicted that in the upcoming debate against Trump "a lot is going to depend upon the rules of the debate, and if she is there for an hour and a half on generally important issues and the questions are fair, she will not be well in a debate setting. She needs her teleprompter. She needs her notes that are probably written by someone else in order to do well."

Cooley and Harris' former aides both said neither had a teleprompter during the AG debate and both had notes on stage.

Former California Assembly Majority Leader Alberto Torrico, who lost to Harris in the primary for the AG race, said it would be a mistake for Trump to assume Harris is "dumb" going into the debate. "She's not dumb, and she's going to prosecute him. She's not going to debate him ... She's going to treat him like one of the defendants that she prosecuted when she was a rank and file DA in Oakland."

A perceived Achilles' heel

Just a few months before the 2010 general election debate, Torrico, former Facebook executive Chris Kelly, Congressman Ted Lieu, former LA City Attorney Rocky Delgadillo and former state assembly member Pedro Nava were among Harris' opponents in the AG primary race.

Congressman Lieu remembered, "She came from a law enforcement background, and that really came out. She didn't take any crap. I wouldn't want to debate her."

Nava was one of the five men who faced Harris in the primary debate held by Los Angeles ABC station KABC. He described her as unfazed, saying, "There's nothing more scary than a woman who doesn't fear men."

Delgadillo, who was next to Harris at the debate, said what stood out to him most was a call she made to him after the race. "She was extraordinarily magnanimous and gracious after defeating all of us," he said.

Torrico said he knew Harris was the frontrunner going into the race.

He said, "The question that I always had in my mind was, can we trap her? Can we get her to say something? Can we get her to lose her cool?"

Torrico said in one forum they were seeking the Service Employees International Union's endorsement. Torrico said he reminded the members in attendance that he had represented many of them, and knowing many spoke Spanish, answered part of a question in Spanish. "They went crazy ... and I just looked at her and I thought, 'Okay, bring it now.'"

He said Harris deflected the original question. "She just went after corporate America and the rich," he said. "She just totally diffused all of the enthusiasm."

"I was just sitting there fuming and saying, 'She's not answering the question at all. I just answered the question. I hit a home run ... and everyone's clapping for you.'"

Torrico said, "I always thought it was an Achilles' heel for her ... she's very good at saying a lot of things without answering the actual question."

He said once at a forum, when he didn't know she was in attendance, he initially felt he had a great response on stage to a question about criminal justice. "I said something like, whoever the next attorney general is, he would have to do such and such." Torrico said Harris "just popped out of nowhere, threw her finger in the air and declared, 'or she will have to!'"

"I was like, 'Oh God, what are you doing here? Where'd you come from?'" said Torrico.

"The room loved it," he said.

Torrico said he grew reflective at the DNC. "I'm among the many people she vanquished on the path to where she is now," he said.

Changing a moment

During her first public office debate for San Francisco district attorney, Harris had been in single digits in the polls, but her former campaign manager says that would change during one of the forums.

Someone in the audience asked Harris how she'd lead independently of the current mayor of San Francisco, Willie Brown. Harris had dated Brown about a decade before when he was the Speaker of California's State Assembly. Harris responded by walking over to her opponents, Bill Fazio and the current DA, Terrance Hallinan, and mentioned the scandals that had been highlighting about each other.

Then she said, "I want to make a commitment to you that my campaign is not going to be about negative attacks."

Former Harris aides say moments like that helped her beat Fazio, and got her to the runoff.

Fazio said he doesn't recall that specific moment, but told ABC News that he had more experience as a trial attorney than Harris. But "she certainly was a much more accomplished and natural politician than I ever was. It's probably the reason I lost."

"She didn't back down"

As the only woman at the time on Howard's debate team, Rosaro-Richardson noticed how Harris challenged men.

"Oftentimes men use their physical prowess and the strength of their voices to win an argument. But I noticed that she didn't allow that to deter her," she said.

She remembers one specific moment when Harris was debating a man during her time on the Howard team.

"She was in cross examination, and [the opponent] hit her hand ... I don't know if it was intentional," she said.

She said Harris stated out loud, "He hit my hand." But Harris, according to Rosario-Richardson, did a "good job of it at the time ... it didn't throw her off. She was able to gather herself back after a few seconds and get back to the point."

Rosario-Richardson said she will be watching Tuesday's debate with other Howard alums and believes Donald Trump will be her most unpredictable opponent yet.

"I would say this is a unique situation because of the unpredictability of how Donald Trump will approach this debate and whether or not she can focus on substantive issues or focus on personal attacks," Rosario-Richardson said.

She added that regardless of having known Harris' debate style for over four decades, she has little idea of what to expect like everyone else. "I'm going to be excited. I'm going to feel some of the anticipation," she said.