A year ago, Hillary Clinton joined me on my radio show for a long discussion about her memoir of the 2016 presidential race, “What Happened?” In September, John Kerry – like Clinton, a former secretary of state – appeared on the show to discuss his memoir “Every Day Is Extra.”

For both former Democratic presidential nominees, it was their first appearance on a program that has run three hours every weekday for over 18 years, on any day of which they would have been welcomed with the same approach: an interview, not a debate.

When he ran for president, Donald Trump joined me by phone more than a dozen times. These were often for long interviews, and never less than 10 minutes. He’s very good at interviews, running over questions he does not care to answer and through journalists who try to steer a conversation artlessly.

Trump won. Clinton and Kerry did not. No, that’s not a correlation of winning the presidency with appearing on my show. Now-Senator-elect Mitt Romney and soon-to-be-retired House Speaker Paul Ryan – the 2012 Republican presidential-vice presidential nominees – were frequent guests in 2012, and they didn’t win. But it is a suggestion to would-be Democratic presidential candidates in 2020 that they all start early to seek out frequent interviews with interlocutors from across the political spectrum in settings that allow for more than a minute’s response.

It doesn’t have to be on my show, though every single one of the two dozen or three dozen serious Democratic would-be nominees is welcome to join me. There are so many serious (and fun) interviews to be had, with straight-down-the-middle journalists such as The Washington Post’s Robert Costa, center-right podcasters including Jamie Weinstein, brilliant young conservatives like Mary Katharine Ham and Guy Benson or long-standing stalwarts of the talk radio world, such as Dennis Prager and myself, who would no more insult a guest than they would their family members at Thanksgiving.

Of course, making the rounds of the Sunday shows will be part of the traditional formula, and sitting down for an amiable chat with a late-night host will stroke some of the base’s erogenous zones, but the real gains are to be made via serious interviews about difficult subjects, sometimes with interviewers who are not likely to be supporters. Some have already realized this: On my program, Rep. Tim Ryan, D-Ohio – who’s expressed interest in running – is already an occasional guest. Though neither are yet declared candidates, Sens. Christopher Coons, D-Del., and Angus King of Maine have also joined me (the latter formally an independent, but so is Sen. Bernie Sanders of Vermont). Both Coons and King would bring quite a lot to the Democratic race, including this willingness to engage.

Political conversation in the U.S. has entered a zone of toxicity I haven’t seen in a broadcast career that began in 1990 and that has always included radio and often television, for every network, and twice as a host for a total of a dozen years on the small screen and nearly 30 over the radio airwaves. It will be tempting to go live on air only in conversation with friends, if not members of the resistance. But not only do independents get to vote in New Hampshire, they also will do so in many other primary contests and, of course, in November 2020.

So seek out the chance to answer tough questions about expanding Medicare or fending off China’s aggression or not withdrawing from the Paris climate pact.

Go in harm’s way, and win votes, and maybe volunteers and donors. I wrote last week that President Trump has become deft at the role of “combatant in chief.” Prepping for him, as for any boxer looking to win a belt, requires a lot of practice sparring. Come early and often, to anywhere you’ll be allowed to make a case for change, not unchallenged but always with a fair chance to answer. There are scores of such places.

Your consultants will say “no.” Take charge of your own campaign and do so with confidence. See you on the air.