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Speculation about when and under what terms President Donald Trump might be interviewed by Special Counsel Robert Mueller has dominated the headlines ever since the two parties began talks in December.

But what about Vice President Mike Pence?

Pence was absent from many of the key incidents Mueller is reportedly investigating as part of his sprawling probe into Russia’s interference in the 2016 election. But he was intimately involved with several, including the firing of former FBI director James Comey, and the subsequent efforts to settle on a rationale for that firing, which appear to be at the center of the Mueller investigation.

So it’s puzzling that Mueller appears to have made no attempt to talk to the administration’s second-highest-ranking official. Pence’s lawyer met with Mueller last year to offer Pence’s full cooperation.

“It’s a bit of a mystery to me that Pence’s name hasn’t really surfaced at all,” Michael Zeldin, a former federal prosecutor who worked closely with Mueller in the Justice Department’s criminal division, told TPM. “There are things that Pence seems to be relevant to. So I’m surprised.”

Pence’s lawyer, Richard Cullen, declined to comment to TPM on the record, while the special counsel’s office declined comment. Pence press secretary Alyssa Farah did not respond to TPM’s request for comment, but in December forcefully denied to CNN that Pence’s office was preparing for a meeting with Mueller.

As of mid-January, NBC reported that the special counsel had made no overtures to Pence about an interview.

By now, over 20 White House officials have been interviewed, including top Trump allies like Jared Kushner, Attorney General Jeff Sessions and White House Counsel Don McGahn. Former chief White House strategist Steve Bannon is scheduled to sit down with Mueller next week.

Former White House lawyers caution that much of what Mueller’s team is up to is happening far from the public eye. After all, one noted, no one saw the indictment of George Papadopoulos coming.

But they offer a few explanations for why Mueller appears to be keeping his distance from Pence, at least for now.

Notably, public reports have offered little indication that Pence is a target of the obstruction of justice, collusion, or money laundering arms of the Russia investigation.

“The reporting so far has revealed not much detail about Pence’s involvement in key events. It may be that, as he did in the case of the the voter fraud commission, he kept his distance and tried to cut his losses. So he will be a witness, but it is hard to say how central to to the case he will be,” Bob Bauer, White House Counsel under President Barack Obama, told TPM in an email.

Pence had not yet joined the team at the time of the June 2016 Trump Tower meeting between high-level campaign officials and Russians promising “dirt” on Hillary Clinton. He was at his son’s wedding in Indiana in late Dec. 2016 when Mike Flynn reached out to then-Russian-ambassador Sergey Kislyak to discuss Obama’s imposition of fresh economic sanctions on Russia. And Pence has maintained he was the last to learn about issues that were either widely reported, like Flynn’s unauthorized lobbying work for Turkey, or that other White House officials were aware of, like Flynn’s conversations with Russian officials during the transition.

Still, there are a few topics that the special counsel would “absolutely” want to talk to Pence about, said Adam Goldberg, White House special associate counsel under President Bill Clinton.

One is what Flynn told Pence about his Russia contacts in January 2016. Flynn was fired in mid-February. The White House has said the firing was because Flynn misled the Vice President about those contacts. But that explanation has generated skepticism, in part because McGahn and Trump reportedly knew by late January that Flynn had lied to both Pence and the FBI.

Mueller might also might want to talk about Pence’s involvement in the May 2017 deliberations over firing Comey. The New York Times reported that Trump informed the Vice President on May 8 that he planned to dismiss the FBI director, reading to him and several other senior officials from a draft memo laying out the case that Comey had mishandled the FBI’s Russia investigation. Trump was stopped from sending that memo out, the Times reported, and instead shifted the justification for Comey’s dismissal onto his handling of the Clinton email investigation. Pence conveyed the official line about Clinton to the press.

Still, as Goldberg noted, other witnesses have likely already provided extensive testimony on these topics, making obtaining Pence’s account less of a priority. Flynn, for example, is cooperating with the special counsel after pleading guilty to lying to the FBI in December.

“If they already have enough people who would testify and aren’t worried about Pence contradicting, from their perspective they’re just going to make a political judgment of, ‘Well we don’t need to go involve the Vice President; that might make us look more partisan,’” he said.

Goldberg, Baeur and Zeldin noted that Mueller’s team is digging through reams of evidence that the public simply doesn’t know about, and that could prompt further lines of questions for the Vice President.

Pence could also serve as a corroborating witness for whatever testimony Trump provides, if he ultimately opts to do so, Zeldin suggested.

But things could get awkward if an invitation is ultimately extended to the Vice President, even as Trump’s own attorneys are reportedly counseling the President not to talk.

“Unless Pence is concerned he’s done something wrong, Pence will appear before Mueller no matter what,” Goldberg said. “Because it’d be political suicide for him not to.”

We just don’t know what he might have to say.