If it wasn’t obvious beforehand, it became clear last week that Ted Cruz is likely to run for president. On Wednesday, the freshman senator’s advisors spilled the beans about his thinking on 2016 to National Review (short version: highly doable), and Friday Cruz showed up in the critical primary state of South Carolina to speak at the state GOP’s “Silver Elephant Dinner.” Which raises a question conspiratorial liberals have been waiting to ask of a Republican since at least 2008: Is Ted Cruz, who was born in Canada to an American mother and a Cuban father, even legally eligible to hold the highest office?

The Constitution says, “No Person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President.” As NBC’s Chuck Todd has pointed out, Cruz’s eligibility would seem to hinge of the definition of the term “natural born.” Is someone who was born abroad so obviously a natural born American?

The consensus among legal experts appears to be, emphatically, “yes.” Here’s Temple University Law professor Peter Spiro, an expert on nationality law, on Todd’s MSNBC show Monday morning:

I think it’s pretty clear that natural born is defined in such a way as to include everybody that has citizenship, and who got it other than through naturalization. So the fact that Ted Cruz had citizenship at birth, and he clearly did under the statute that applied at the time, it’s pretty clear that he qualifies as natural born.

But it turns out that there’s at least one legal heavyweight who would question Spiro’s argument—a guy who goes by the name of … Ted Cruz.

Here’s Cruz’s problem: Under further questioning, Spiro conceded that Cruz’s case isn’t really clear cut if you limit yourself to the actual wording of the Constitution. (The Constitution never defines what “natural born” means.) Rather, what makes Cruz’s eligibility a no-brainer is the way the country has chosen to interpret the Constitution in recent decades. “It’s a question of how our understandings have evolved over time,” Spiro said. “So the examples that you cited in the setup—George Romney, John McCain, Barry Goldwater—all pretty clearly establish that the American people are on board with somebody who was born outside of the United States, but who had citizenship at birth.”