Democrats are up in arms over the way House Intelligence Committee chair Rep. Devin Nunes (R-CA) has handled its investigation into Russian interference in the 2016 election, with several members demanding he recuse himself.

Nunes, in turn, complained Wednesday to NBC News that Democrats “aren’t really serious about this investigation” and have not fully participated in committee efforts.

Tensions with Nunes spiked after a press conference last week in which he revealed he went around the committee to obtain evidence that court-approved spying on foreign targets had scooped up “incidental” surveillance involving people associated with Trump. There’s also an ongoing feud over a decision by Nunes to cancel a series of hearings on the issue.

Here are the big outstanding questions driving the story.

What did Nunes learn and why did he change his story?

Nunes said initially at his press conference that he had seen materials that “clearly show the president elect and his team were at least monitored” during the transition. But two days later he said he was not sure whether Trump and his aides were monitored and a spokesman said he needed to review more information. The rest of the committee has not viewed the documents in question.

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Who was Nunes’ source?

On the day before his press conference, Nunes met with an unnamed source at the White House. This fueled speculation that a White House official had provided the information to Nunes to bolster the president’s tweeted claim that President Barack Obama illegally ordered surveillance, which had been repudiated by the nation’s highest intelligence and law enforcement officials, as well as by Nunes himself. Nunes has not shared his source with fellow committee members, but told Bloomberg columnist Eli Lake it was an intelligence official and not a White House staffer.

Why did Nunes visit the White House?

Nunes says he only met his source at the White House in order to use a secure facility (known as a SCIF) for viewing sensitive intelligence. Congress has similar facilities, however, and Democrats are raising questions about why he was there and whom he met during his visit. Nunes says the reason he had to use the White House SCIF was because the material was not accessible by computer in Congress.

White House Press Secretary Sean Spicer told reporters on Wednesday he did not have an answer as to who signed Nunes into the White House and that he did not personally know the source of his information. Nunes has also told NBC News he did not reveal his source to Trump.

Former White House officials have told NBC News that the administration should be able to quickly discern who signed Nunes into the building. The Trump White House has not publicly released visitor logs in general, which previous administrations have done.

Why did Nunes cancel a series of hearings? And will they be rescheduled?

In recent days, there’s been a feud between Nunes and Democrats on the committee over a decision to scrap a planned public hearing with witnesses, including former Director of National Intelligence James Clapper, former CIA director John Brennan and former acting Attorney General Sally Yates.

Democrats have accused Nunes of trying to suppress their testimony, especially after a series of letters surfaced in which Yates’ attorney complained they had not been given clearance by the White House and Justice Department to discuss unclassified conversations related to a senior official, presumably former National Security Adviser Michael Flynn. The White House has said the letters were misinterpreted and that Yates was always welcome to testify, including on the matters described in the letter. Nunes also said the committee “asked her to testify on our own accord and we still intend to have her speak to us."

Nunes said the plan was to further question FBI Director James Comey and NSA director Mike Rogers instead, but then postponed that hearing as well, citing scheduling issues. A series of additional meetings were postponed as well. Democrats say that explanation doesn’t add up and want the hearings immediately rescheduled. Rep. Eric Swalwell (D-CA), a member of the intelligence committee, told MSNBC on Wednesday that "no future hearings for the Russia investigation are on the books."