Harris’s Debate Tutor: a Lawyer Unafraid of Telling Politicians Hard Truths

Vice President Kamala Harris has never met or spoken with former President Donald J. Trump, but the woman running her debate preparations has spent a lot of time thinking about how to respond to what Republican nominees say during an onstage clash.

That outside Harris adviser, Karen L. Dunn, a high-powered Washington lawyer, has trained Democratic presidential and vice-presidential candidates for debates in every election since 2008.

She is described by candidates she has coached and other people who have worked with her as a skilled handler of high-ego politicians. By all accounts, she possesses the rare ability to tell them what they are doing wrong and how to fix it — and how to inject humor and humanity to sell themselves to voters watching the debate.

“It’s a combination of tough love,” Hillary Clinton, whom Ms. Dunn helped prepare for presidential debates in 2008 and 2016, said in an interview on Thursday. “She’s unafraid to say, ‘That’s not going to work’ or ‘That doesn’t make sense’ or ‘You can do better.’ But she also offers encouragement, like, ‘Look, I think you’re on the right track here’ and ‘You just need to do more of that.’”

The emergence of Ms. Dunn as the leader of Ms. Harris’s debate team comes at a critical moment in both the presidential race and Ms. Dunn’s professional life.

When she is not preparing top Democrats for debates — in addition to her four previous cycles of involvement at the presidential and vice-presidential level, she has worked with Senators Mark Warner of Virginia and Cory Booker of New Jersey — Ms. Dunn is a top lawyer for some of America’s leading technology firms.