RACHEL MARTIN, HOST:
Senator Cory Booker is the latest Democrat to make it official.
(SOUNDBITE OF POLITICAL AD, "TOGETHER, AMERICA, WE WILL RISE")
CORY BOOKER: Together we will channel our common pain back into our common purpose. Together, America, we will rise. I'm Cory Booker, and I'm running for president of the United States of America.
MARTIN: The New Jersey senator made a name for himself as the mayor of Newark. He is the fourth senator to run for the Democratic nomination, and he probably will not be the last. That's a safe bet. NPR's Scott Detrow is covering the growing 2020 presidential campaign and joins us in the studio. Good morning, Scott.
SCOTT DETROW, BYLINE: Good morning.
MARTIN: We had expected this. Cory Booker had been hinting not-so-subtly that he was interested in a presidential run. What is his message out of the gate as he launches?
DETROW: You know, so far, candidates like Kamala Harris and Kirsten Gillibrand, two other senators running, are framing themselves as fighters, people who will stand up to Donald Trump. Booker is taking a different tact. That's been a big part of his political career. He certainly can be confrontational. Anyone who saw him in the Brett Kavanaugh confirmation hearing saw that. But Booker has long stuck to big, sweeping themes like unity, common purpose, a sunny, positive approach most of the time. He seems to be making a bet to the pendulum theory of politics here that after years of President Trump being divisive and focused on the base, that Americans would be interested in the opposite approach.
MARTIN: So what are some of the challenges that he's going to face?
DETROW: Well, first of all, you mentioned it's a big field that's going to keep getting bigger. Booker has been a high-profile Democrat for years. He was on Hillary Clinton's shortlist for vice president. For a long time, there's been a flip side to Booker's high media profile. There's been a lot of progressive skepticism of Booker, especially as the party has gotten more populist. He's from New Jersey, and therefore, he's had close relationships with big industries in that area - Wall Street, the pharmaceutical industry.
DETROW: That's something that comes up a lot from his critics. Booker has sponsored bills to legalize drug imports from Canada in recent years, among other steps, but that's something that that always comes up from the critics.
MARTIN: As we note, he's going to have to distinguish himself because there are a lot of folks who have also thrown their hat in the ring - a lot of his Senate colleagues. How does he do that in such a large field?
DETROW: It's a great question. For a long time, Booker has distinguished himself on social media. Before President Trump made Twitter central to his political identity, Booker did - of course, in a very different way. You may remember back when he was mayor of Newark - you know, responding to requests from constituents, like, hey, can you come shovel my driveway? And he'd show up and do it and post about it on Twitter.
DETROW: He's kept that up in the Senate. I'm curious to see how that translates to a national campaign. He's carved out a very progressive space in the Senate, pushing for marijuana legalization, criminal justice reform. He played a big role in the law signed a couple months ago - guaranteed jobs plan. But of course, most of the candidates running have very progressive stances. Booker's entrance highlights what a large field it is, but also how diverse this field is. Of the four U.S. senators running, you have three women and one African-American man. None of the four U.S. senators running are white men at this point, and that is certainly very different from centuries of American presidential politics.
MARTIN: Right. So speaking of that - Joe Biden, Bernie Sanders. When are we going to hear from them?
DETROW: That is the big question. You mentioned that we expected Booker to enter the race - same with a lot of the other candidates who entered. Biden - there's a big question of whether or not he's going to do it, and Bernie Sanders, increasingly, as well. There are questions of, does he run again, or does he sit - play a kind of a kingmaker role now that so much of the party has been molded in his policy image?
MARTIN: All right. NPR's Scott Detrow. Thanks so much. We appreciate it, Scott.
DETROW: Thank you.