As the Republican primaries approach, Donald Trump is questioning whether Ted Cruz, who was born in Canada to an American mother, is eligible to serve as President. PHOTOGRAPH BY SCOTT OLSON / GETTY

Every U.S. Presidential election is a debate about the character of the American people. We elect the candidate who tells us, to our greatest satisfaction, what the American people stand for. We vote for a vision of ourselves. This election cycle, though, the debate has been less about who the American people are than about who the American people are not.

Among the not-Americans are immigrants, refugees, and asylum seekers. Presidential candidates have proposed building walls along the nation’s borders, applying religious tests at immigration centers, and deporting as many as eleven million undocumented immigrants. The not-American people even include citizens who might seek to hold elective office. Ben Carson has said that he “would not advocate that we put a Muslim in charge of this nation.” He was speaking in defiance of Article II, Section 2 of the Constitution, which establishes only these requirements for that office:

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; neither shall any Person be eligible to that Office who shall not have attained to the Age of thirty five Years, and been fourteen Years a Resident within the United States.

The attention that Donald Trump has lately been paying to Ted Cruz’s eligibility for the Presidency defies the Constitution, too, at least in spirit. That spirit was captured by James Madison in Federalist No. 52, where, regarding the qualifications for members of Congress (you’ve got to be twenty-five, have been a U.S. citizen for seven years, and live in the state you propose to represent), he wrote, “Under these reasonable limitations, the door of this part of the federal government is open to merit of every description, whether native or adoptive, whether young or old, and without regard to poverty or wealth, or to any particular profession of religious faith.” The requirements for the Presidency are suffused with this same spirit; the residency period is longer, and “natural born” was added at the last minute. But the door is meant to be open. Still, while questioning Cruz’s eligibility is constitutionally ill-considered, it isn’t a wayward Trump stunt, like his demand for Barack Obama’s birth certificate. It is, instead, wholly consistent with the message of the leading G.O.P. candidates in 2016: America is closed.

Ted Cruz was born in Canada, in 1970, to an American mother and a Cuban father. He has been a U.S. citizen since his birth under the terms of a law that grants citizenship to any child “hereafter born out of the limits and jurisdiction of the United States,” so long as one of the parents is an American citizen. He is an American. Is he a “natural born citizen”? In 1787, the phrase was inserted into the draft of the Constitution, without recorded debate, after John Jay wrote a letter to George Washington suggesting that “it would be wise and seasonable to provide a strong check to the admission of foreigners into the administration of our national government and to declare expressly that the commander in chief of the American army shall not be given to, nor devolve on, any but a natural born citizen.” The phrase “natural born citizen” is one of the sloppiest in the Constitution. It’s not the same as the “natural born subject” of English common law and Blackstone’s “Commentaries,” meaning those born within the king’s realm or, depending on the circumstances, outside the king’s realm but to the king’s subjects; Americans were, of course, rejecting the fealty of blood. The “natural born citizen” requirement, while much discussed, has never been resolved. It has dogged many a candidate, including Barry Goldwater, who was born in Arizona before it became a state, and John McCain, born on an American military base in the Panama Canal Zone. In both cases, the thinking was, generally, that these men were eligible for the office. Goldwater and McCain were both the children of U.S. citizens. Far less compelling arguments have been made for a constitutional amendment in order to advance the political careers of Henry Kissinger and Arnold Schwarzenegger, who were both born outside the United States to non-American citizens and, by any possible construction of the clause, are ineligible for the Presidency. Cruz’s case is slightly weaker than those of Goldwater and McCain (because the places where they were born were at least arguably under American jurisdiction), and it’s possible that confirming his eligibility could require a court decision. That would be ironic, given the place of citizenship laws in the current political debate, if, sadly, fitting.

Politics is the art of describing how the world came to be the way it is in such a manner as to convince people that you know how to make the world the way it ought to be. “Make America Great Again” does that work in four words, a “Keep Out” sign in just two. Citizenship laws are a product of politics, and, as the political scientist Rogers Smith argued in his magisterial study, “Civic Ideals: Conflicting Visions of Citizenship in U.S. History,” the contraction of citizenship closely tracks with the realignment of political parties. When Americans are most divided politically and the parties are rearranging themselves, the doors to entry tend to swing shut, with “the American people” on one side, everyone else on the other.

That political division should result in disenfranchisement and immigration restriction is, at first, surprising: Why wouldn’t a period of polarized politics result, at least sometimes, in the liberalization of citizenship laws? Smith’s analysis suggests two answers. First, party realignments of the sort that we’re in the middle of tend to have a conservative effect on citizenship laws because they tend to follow eras of democratizing political reform characterized by the expansion of suffrage; the conservative answer to advances of egalitarianism is to try to reverse them by restricting voting rights and immigration. Reconstruction reshaped citizenship laws, enfranchising black men and speeding up the race for female suffrage. It also marked the beginning of decades of backlash that, in practice, denied the right to vote to black men and fuelled anti-immigration fires that resulted in the Chinese Exclusion Act of 1882 and the Immigration Act of 1924. The civil-rights movement of the nineteen-fifties and sixties was followed by the conservative era in American politics that began in 1964. But a second reason that periods of political realignment tend to track with restrictions on citizenship, Smith argues, is that liberal democrats are very bad at talking convincingly about citizenship because doing so well requires invoking “the American people,” and liberal democrats would rather talk about humanity. “The failure of liberal democratic civic ideologies to indicate why any group of human beings should think of themselves as a distinct or special people is a great political liability,” he writes. Unifying the electorate, like reforming citizenship laws, requires invoking “the American people,” which is something liberals tend to be very bad at.

Ted Cruz is not a foreigner in anything like the way John Jay understood a foreigner. If elected, he should be allowed to hold office. To cling to the narrowest possible meaning of “natural born citizen” is to cling to the narrowest possible understanding of citizenship. That may be what Cruz himself is doing. But it’s not what the American people stand for.