The House Intelligence Committee just finished hearing from a dozen witnesses, many of whom said President Trump’s allies were pushing unsubstantiated allegations about Joe Biden in Ukraine. Now, a Ukrainian American who worked with Trump attorney Rudolph W. Giuliani says he wants to testify that the top Republican on the committee was helping them dig up dirt on Biden, too.

That’s the allegation now facing Rep. Devin Nunes (R-Calif.): that he was in on the very thing Congress has launched an impeachment inquiry into Trump over. Nunes has said stories reporting this are “demonstrably false."

Let’s review the allegation, the players, what Nunes has said about all this and what Democrats might do to look into it.

The allegation

That Nunes and/or his staff met with Ukrainian officials whom witnesses have described as “corrupt.”

The allegation comes from Lev Parnas, a business associate of Giuliani’s. Through a lawyer, Parnas is saying he would be willing to testify under oath that Nunes was working with them to damage Biden before the 2020 election. Parnas has produced thousands of pages of documents and even video about his work with Giuliani in Ukraine. We don’t know what, if anything, these documents say about Nunes.

CNN first reported Friday night that Parnas would be willing to testify that Nunes traveled to Vienna last year to meet with former Ukrainian prosecutor general Viktor Shokin. CNN looked at congressional travel records and noted that Nunes traveled to Europe around that time on a taxpayer-funded trip.

Shokin is the prosecutor Biden pressed Ukraine to remove in 2016 because he wasn’t doing adequate work to prosecute corruption. At the time, Biden was working on having Shokin removed, his son Hunter Biden served on the board of a Ukrainian energy company, Burisma, which had once been under investigation and which has a known history of corruption. There is no evidence that Hunter Biden acted illegally or that Joe Biden was acting to influence policy toward Burisma.

But it wasn’t just this one trip Nunes is alleged to have been involved in. Parnas’s lawyer said his client would testify that a Nunes aide talked over Skype with Ukrainian officials who have pushed theories about Democrats working in Ukraine during the 2016 election.

That comes from CNBC, which reported that Parnas would be willing to testify Nunes aide Derek Harvey wanted to travel to Ukraine for this but scrapped the trip after he realized he would have to report it to the top Democrat on the committee, House Intelligence Committee Chairman Adam B. Schiff (D-Calif.). Instead, they talked over Skype, according to Parnas’s allegation.

Parnas’s attorney told The Washington Post that Harvey met with his client, Giuliani and their associates this spring at the Trump hotel in Washington to talk about Biden.

If these allegations are true, it would mean a powerful member of Congress who is deciding whether to impeach Trump over pressuring Ukraine attempted to help Trump by working to further his political goals in Ukraine.

What Nunes has said about this

Nunes has said stories reporting this are false but didn’t explicitly deny the allegations.

He described the reports as “fake” and “demonstrably false and scandalous stories,” and threatened to sue the Daily Beast and CNN, which led the way on reporting about this. (It would be a very heavy lift to win those lawsuits, given that Nunes is a public figure and would have to prove malicious intent.)

But he refused to answer a question about whether he did what he’s accused of doing.

Here’s Maria Bartiromo asking him Sunday on Fox News whether he met with Ukraine’s former prosecutor in Vienna last year, for any reason.

BARTIROMO: Bottom line, were you in Vienna with Shokin?
NUNES: Yes, so, look, Maria, I really want to answer all of these questions.
And I promise you I absolutely will come back on the show and answer these questions. But because there is criminal activity here -- we're working with the appropriate law enforcement agencies. We're going to file all this. Everyone's going to know the truth. Everybody's going to know all the facts.
But I think you can understand that I can’t compete by trying to debate this out with the public media when 90 percent of the media are totally corrupt.

Shokin denied that he met with Nunes.

Who’s making these allegations again?

Parnas is a Ukrainian American whose lawyer said he worked with Giuliani over the past year to try to find damaging information about Biden in Ukraine, with the goal of ousting then-Ambassador Marie Yovanovitch. Parnas and another associate, Igor Fruman, were recently indicted here in the United States on campaign finance charges related to removing Yovanovitch.

Yovanovitch testified that she thought their financial interests were threatened by her anti-corruption campaign in Ukraine.

Parnas has a motive for talking now: He has pleaded not guilty, and his lawyer told the New York Times that Parnas “reasonably believed Giuliani’s directions reflected the interests and wishes of the president” and that he is “remorseful for involving himself … in the president’s self-interested political plot.”

From there, it’s not a big leap to assume that Parnas could try to leverage his goodwill with Congress to the courts to get a lesser sentence.

What could happen to Nunes

Maybe nothing. It’s not clear that Parnas will get to talk to Congress about Nunes. Schiff hasn’t said whether he would reopen hearings to listen to the allegations. His committee has already started writing a report on what they found, and Democrats are on a tight timeline to finish their impeachment investigation before 2020.

Some Democrats in Congress are saying they want a bipartisan panel in the House to investigate what Nunes did, on the grounds that he was using taxpayer money for a political purpose. That’s possible. Though we should note an ethics investigation in 2017 looked at whether Nunes improperly gave Trump a heads-up on what the House Intelligence Committee was investigating, with classified documents. The committee cleared him of wrongdoing.

Right now, it remains Nunes’s word against that of an accused criminal.