AUDIE CORNISH, HOST:
Surprising news today from John Bolton - he ran the White House National Security Council until September. That's where he had a ringside seat to the events that led to President Trump's impeachment. House Democrats hoped to hear from Bolton last year, and at the time, he declined. But today Bolton said he would be willing to testify at Trump's impeachment trial in the Senate.
Mara Liasson, NPR national political correspondent, has been following the twists and turns of this. Welcome to the studio.
MARA LIASSON, BYLINE: Thanks for having me.
CORNISH: What changed? Why is Bolton saying he's willing to testify in a Senate trial?
LIASSON: We're not sure why he's changed his mind, but what changed was - he was involved in a court challenge to a subpoena that had been given to his longtime aide Charles Kupperman, and Kupperman went to court. He sued the White House and the House. He said, there's a separation of powers clash. The judicial branch has to referee this. I will honor the subpoena only if a judge tells me to. And Bolton had said that whatever the judge decides would apply to - he would apply to himself also if he got a subpoena from the House.
Well, lo and behold, the House withdrew the subpoena. They might have been worried about losing the case. And the judge declared that case moot. Now Bolton has issued a statement saying since his testimony once again is at issue, he has - based on careful consideration and study, he's concluded that if the Senate issues a subpoena for his testimony, he will testify. He won't go to court to challenge it. He will just honor the subpoena. That's what's new.
CORNISH: But he's saying this while the Senate is in this back-and-forth about how a trial would go, right? I mean, what are the chances that he would even be subpoenaed?
LIASSON: I think the chances are pretty slim. Now, the Democrats - Senator Chuck Schumer has said he wants to hear testimony from Bolton and other White House officials. Remember, Republicans complained repeatedly that the House didn't have enough firsthand witnesses in the impeachment inquiry. Of course, that's because the White House blocked almost anyone with firsthand knowledge from testifying. Bolton is one of those people. He had conversations with Donald Trump about the frozen aid. He is the highest-ranking White House official that we know, from testimony from his former aides, was trying to get the aid released. He very famously described the hold-up of the aid as a drug deal that he didn't want any part of.
But Mitch McConnell, the Republican leader, has said it's too early to talk about witnesses. He said, after the opening statements, then we can talk about witnesses. And even if Bolton was subpoenaed, the White House could go to court to stop the subpoena and say that Bolton was covered by this broad executive testimonial immunity and doesn't even have to show up.
CORNISH: We know that Bolton was concerned, at least, about how Ukraine policy was being executed. I want to go back to how Fiona Hill, the Russia expert at the NSC, described him in her testimony before the House.
(SOUNDBITE OF ARCHIVED RECORDING)
FIONA HILL: Ambassador Bolton had looked pained - basically indicated with body language that there was nothing much that we could do about it. And then, in the course of that discussion, said that Rudy Giuliani was a hand grenade that was going to blow everyone up.
CORNISH: So if John Bolton did testify, is there any sense that he'd be a good witness either for Democrats or in defense of the president?
LIASSON: Well, that is a good question. Democrats clearly assume he'd be a good witness for them based on what Hill testified and what other aides said. He wasn't a fan of Rudy Giuliani freelancing on Ukraine policy. He certainly wanted aid to go to Ukraine because they were involved in a hot war against Russia. But there's no guarantee he would be a great witness for Democrats because he might very likely claim executive privilege for any conversations he had with the president.
CORNISH: What should we know about him - a little bit of context to give us a idea of why this is happening.
LIASSON: He's a longtime foreign policy hawk, very conservative on Iran, North Korea and Russia. He's also a player in conservative politics. He has a couple superPACs. He certainly believes the president should have broad immunity - a president, any president. We don't know exactly why he's coming forward at this time. We do know he has a book coming out in the spring that is expected to cover his time in the Trump administration.
CORNISH: NPR's Mara Liasson, thank you.
LIASSON: Thank you. Transcript provided by NPR, Copyright NPR.