The White House pushed back against his claims.
"As we've said many times before, there was no collusion with the Trump campaign," White House press secretary Sarah Sanders said on Monday. "Anything further on what his actions are, he hasn't worked at the white house, so I certainly can't speak to him or the lack of knowledge that he clearly has.
Nunberg’s brief time on the Trump campaign ended in August 2015 when he was fired after multiple racially charged Facebook comments were discovered on his personal account. The posts even included a slur directed at former President Barack Obama. In the summer of 2016, Trump sued Nunberg for $10 million violating a non-disclosure agreement by leaking confidential information about the campaign to the media.
Nunberg denied the allegation and the suit was later settled for an undisclosed amount.
Asked during the White House briefing on Monday about Nunberg's claim that the president may have done something wrong during the campaign, Sanders maintained that there was absolutely no collusion by the Trump campaign, but wouldn't comment further on Nunberg specifically, noting that he's not a White House official.
"I definitely think he doesn't know that for sure because he's incorrect. As we said many times before, there was no collusion with the Trump campaign," Sanders said. "Anything further on what his actions are, he hasn't worked at the White House. So I certainly can't speak to him or the lack of knowledge that he clearly has."
Nunberg’s media scramble Monday began with an interview with The Washington Post, during which he said the special counsel had summoned him to meet with the grand jury on Friday and announced his intention not to cooperate any further with the special counsel.
“Let him arrest me,” Nunberg told the Post. “Mr. Mueller should understand I am not going in on Friday.”
It is unclear what, if any action, the special counsel could potentially take against Nunberg for failing to comply with the subpoena. Special counsel spokesman Peter Carr declined to comment on Nunberg’s repeated suggestions he would defy lawful subpoenas for records and an appearance before a grand jury.
Appearing first on MSNBC, then three times on CNN, Nunberg bemoaned the amount of time and money on legal fees he felt cooperation with the special counsel’s “witch hunt” investigation required.
In one of Nunberg's appearances Monday on CNN he alluded to Trump being aware of the infamous June 2016 meeting at Trump Tower with Russians. But Nunberg later told media outlet Vox that he had "no special knowledge" Trump was aware of the meeting and his comments were being misinterpreted.
Democratic Rep. Adam Schiff, ranking member of the House Intelligence Committee, told reporters Monday they want to speak with Nunberg, while Rep. Mike Conaway, R-Texas, the Republican leading the House investigation, said he hadn't heard of Nunberg and wouldn't say if the committee wanted to interview him.
“Certainly if Mr. Nunberg has light to shed on what the president knew before the Trump Tower meeting we’d be interested in finding out,” Schiff said, referring to Nunberg's claim that Trump was aware of the June 2016 meeting.
“He is among a frankly fairly large group of witnesses that we still need to bring before our committee,” he added, saying the majority hasn’t agreed to do so.
Schiff wouldn’t say if he believes that the president knew about the Trump Tower meeting, but said he believes Donald Trump Jr. and other campaign officials viewed it as a serious undertaking.
He said there’s also interest in questioning Nunberg about Roger Stone’s communications with WikiLeaks, given their close association. Stone, a longtime associate of Trump and mentor to Nunberg, met with the House Intelligence Committee last September.
ABC News' Ben Siegel contributed to this report.