As Joe Biden edges closer to a presidential run, there’s no shortage of theories as to what he’s up to. Former secretary of state Hillary Clinton has built a commanding lead in the national polls, giving Biden little apparent space to gain traction. Perhaps he’s counting on the early-primary state of South Carolina to provide a critical boost. He might be banking on appearing as a stronger general-election candidate than any of his potential rivals in the primary race. Maybe after spending the past 42 years of his life running for elective office, he just can’t stop.

But there’s one intriguing theory that has so far garnered little attention: What if Biden knows something about Democratic frontrunner Hillary Clinton that the rest of us don’t?

After jumping to what seemed a prohibitively large early lead, Clinton has stumbled in recent months. Vermont Senator Bernie Sanders, hardly the most charismatic politician, has emerged as a viable challenger, generating enormous enthusiasm on the campaign trail, and surging ahead in polling averages in New Hampshire.

Clinton, meanwhile, is battling a steady drip of negative headlines and revelations stemming from her use of a private email address and server during her term as secretary of state. Investigators have found that some emails contained information that was later classified, and media reports have suggested that some of this information may have been considered classified at the time it was shared, even if it hadn’t yet been labeled that way.

The emails that Clinton gave to the State Department are now being released in tranches every 30 days. Her server has been turned over to the Justice Department, which is reportedly optimistic that it can recover at least some of the emails that Clinton had deleted. No one knows what the emails that have not yet been released may contain.

No one, that is, outside of the administration. Those on the other end of Clinton’s correspondence presumably retain their own records of their exchanges. The White House has reportedly monitored the situation since before the questions over Clinton’s email became public. And the State Department has assigned a team to sort through the emails, reviewing them for classified information.

Clinton, and her loyalists, insist that the email probe is a distraction, and that there is no evidence that she deliberately broke any rules, much less violated the law. And so far, those claims have been borne out by each new round of disclosures.

If that’s not the case, though—if the emails contain revelations that are embarrassing, or worse—there’s a limited number of people who might be in a position to know it. Clinton’s own aides top the list. So do various White House officials.

And then, of course, there’s the State Department. Biden forged many relationships during his long tenure in the Senate, and State is chock full of longtime friends and former aides. The current deputy secretary of state, to choose the most prominent example, is Antony Blinken. He was hired as the staff director of the Senate’s foreign relations committee in 2002, and senior adviser to its senior Democratic member: Joe Biden. He stuck with Biden through the 2008 campaign, first becoming his national security adviser in the White House, then moving over to become Obama’s deputy national security adviser in 2013, and finally taking up his current role at the State Department in 2015. “I have now had the good fortune to work alongside Tony Blinken for many years,” Biden said when he was nominated for the State Department position. “He is a good man. I’m proud of him.”

There’s no reason to think that Blinken, or any of Biden’s other contacts within the White House or the national-security establishment, have shared with the vice president any information to which they’re privy. In fact, in late June, Blinken and his wife, another former Biden aide who’s now an assistant secretary of state, both gave the maximum allowable donation of $2,700 to Clinton’s campaign.

But if Biden seems more confident than most pundits that Hillary Clinton’s nomination isn’t inevitable, it may reflect more than his natural ebullience and legendary optimism. It may be a sign that he’s banking on voters learning things that he already knows.