AUDIE CORNISH, HOST:

President Trump's former campaign manager, Corey Lewandowski, testified on Capitol Hill today. Lewandowski is known for his fierce loyalty to the president, and his testimony before the Democratic-led House Judiciary Committee got testy. NPR justice reporter Ryan Lucas watched the hearing. He joins us now.

Welcome to the studio.

RYAN LUCAS, BYLINE: Thank you.

CORNISH: First, why was he there? Why did Democrats want to talk to Corey Lewandowski?

LUCAS: So this hearing is part of what Democrats have taken pains to call an investigation to determine whether to recommend articles of impeachment against President Trump. Now, Corey Lewandowski appears quite a bit in the Mueller report. Importantly for Democrats today, Lewandowski was a witness to one of the key episodes, really, in the investigation of possible obstruction of justice by the president. And that episode was in June of 2017 when Trump asked Lewandowski to deliver a message to then-Attorney General Jeff Sessions, basically to have Sessions limit the Russia investigation. Lewandowski, according to the report, never actually delivered that message. Democrats, though, subpoenaed him to hear about that episode. The White House, though, directed Lewandowski before this hearing not to answer questions about his discussions with the president or any administration officials not in the Mueller report. And Lewandowski really leaned on that a lot today.

(SOUNDBITE OF ARCHIVED RECORDING)

COREY LEWANDOWSKI: Congressman, the White House has directed I not disclose the substance of any discussions with the president or his advisers to protect executive branch confidentiality...

Congressman, the White House has directed I not disclose the substance of any discussion with the president...

The White House has directed me that I not disclose the substance of any conversation...

LUCAS: So this clearly frustrated Democrats today, particularly because Lewandowski was never a member of the administration. They say that there's no legal basis for this privilege. Democrats also pointed, though, that this is an example of what they say is the president's obstruction of congressional oversight. Lewandowski was appearing under subpoena. Democrats had subpoenaed two former White House staffers as well, Rick Dearborn and Rob Porter. Neither one of them showed up because the White House says those two are immune from testifying because they're former administration officials.

CORNISH: And yet Lewandowski did show up. What more did he have to say?

LUCAS: Well, there weren't really any factual revelations today. What was striking about this hearing, really, was the tone. Lewandowski is an ardent supporter of the president, and he's known for being pretty combative. And this hearing, as you noted earlier, did turn testy. Take a listen to this exchange from very early on between the Democratic chairman, Jerry Nadler, and Lewandowski.

(SOUNDBITE OF ARCHIVED RECORDING)

JERRY NADLER: But I simply ask you, is it correct that, as reported in the Mueller report, on June 19, 2017, you met alone in the Oval Office with the president?

LEWANDOWSKI: Could you read the exact language of the report, sir? I don't have it available to me.

NADLER: I don't think I need to do that, and I have limited time. Did you meet alone...

LUCAS: Now, there was sniping from Republicans as well. They accused Democrats of basically wasting committee time, of rehashing things that were already covered in the Mueller report and that had been discussed in public for months, really.

CORNISH: You said earlier this was part of what the Democrats are calling an impeachment investigation. Where does this investigation go from here?

LUCAS: So the committee already heard from Robert Mueller. Of course, that was in July. Lewandowski was the first fact witness from Mueller's report to testify before the committee. Democrats are still fighting in court to get another witness - that's former White House counsel Don McGahn - to testify. The White House has blocked him from testifying. So the Democrats' investigation has had trouble really picking up any steam. Now, for Lewandowski, he's considering a Senate run in New Hampshire next year. He actually used a five-minute break during the hearing today to tweet about a new website that he just launched for that potential Senate run.

CORNISH: NPR justice reporter Ryan Lucas, thanks so much for explaining it.

LUCAS: Thank you. Transcript provided by NPR, Copyright NPR.