There’s a long-running theory that Mark Zuckerberg has presidential aspirations. It makes sense to wonder. After all, if the civically engaged and ambitious billionaire leader of the most powerful media company on the planet wanted to take on a new challenge, why not try running a country? It’s not like he has many other opportunities for a promotion.

But only in recent weeks has a Zuckerberg run for the American presidency started to seem like a legitimate possibility. First there was his personal challenge for 2017: Zuckerberg’s aiming to visit and meet with people in all 50 states by the end of the year.

And not just that, but he framed the exercise in a way that sounds, well, political:  “Going into this challenge, it seems we are at a turning point in history,” he wrote in a Facebook post. “For decades, technology and globalization have made us more productive and connected. This has created many benefits, but for a lot of people it has also made life more challenging. This has contributed to a greater sense of division than I have felt in my lifetime. We need to find a way to change the game so it works for everyone.”

Another post, which Zuckerberg published on Facebook last night, has a similarly campaign-esque vibe to it:  

“Heading back home after a great few days in Texas. Today we drove down to Waco and stopped in smaller towns along the way. I had lunch with community leaders in Waxahachie who shared their pride in their home and their feelings on a divided country. I met young moms in West who moved back to their town because they want their kids to be raised with the same values they grew up with. And I met with ministers in Waco who are helping their congregations find deeper meaning in a changing world ... We may come from different backgrounds, but we all want to find purpose and authenticity in something bigger than ourselves.”

He also announced he’s starting a Facebook page for photos from his travels in 2017, which is another thing a political candidate would do.

And back in April, buried in a clause in this SEC filing from Facebook, was another clue: “Mr. Zuckerberg’s leave of absence or resignation would not constitute a Voluntary Resignation if it were in connection with his serving in a government position or office.”

If Zuckerberg decides to run for president in 2020, no one who’s paying attention will be shocked. (For what it’s worth, the tech columnist Nick Bilton, writing for Vanity Fair, suggests it’s more likely that the 32-year-old Zuckerberg would run in 2024.)

And if Zuckerberg is indeed laying the groundwork for a possible run for office, the role of Facebook during such a race raises several huge questions. Facebook is a dominant force in the flow of news and information, and its engineers can—with the tweak of an algorithm—grab the attention of its users on a massive scale. Facebook can even toy with its users emotions, as a secret mood manipulation study revealed in 2014. So there are several ways that Facebook could use its power to skew an election, and that’s before considering how much personal data it has on the American people: Facebook, in the hands of a political operative, would put ordinary voter rolls to shame.

That’s not to say that Zuckerberg would use this data improperly—or at all. (We don’t even know if—or when—he’s actually considering running for office! Facebook didn’t immediately respond to a request for information about Zuckerberg’s potential political goals.) But it does help highlight why people ought to begin thinking through the implications of a possible Zuckerberg presidential run.

After all, journalists started casually asking Donald Trump whether he might run for president in the 1980s. Tomorrow he takes the oath of office.