A droll Politico headline earlier this week nicely summed up the state of bemusement and incomprehension surrounding the Republican Party’s revived fixation with ending birthright citizenship.

“Trump to O’Reilly: 14th Amendment is unconstitutional.”

Fox News' Bill O’Reilly grilled Trump on Tuesday, based on the widely shared premise that ending birthright citizenship would require changing the Constitution to excise or edit the first sentence of the Fourteenth Amendment. That sentence states, “All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.”

Republicans are racing to catch up with Trump, creating a fresh consensus among the party's presidential candidates that birthright citizenship is bad, and a presumption among most critics and reporters that these candidates believe the Constitution is flawed, and should perhaps be changed.

Neither of these presumptions necessarily describes anti-birthright candidates. Many Republican presidential hopefuls share the belief that giving the children of immigrants citizenship automatically is bad. In less abstract terms, they’re affirming an unfounded nativist anxiety that birthright citizenship creates an incentive for child-bearing immigrants to stream across the border and secure all the benefits of citizenship, including welfare, for their offspring—what conservatives derisively refer to as “anchor babies." But they disagree among themselves over how to address the problem. And because the point of contention is so politically toxic—a dramatic shift to the right relative to the also-toxic Republican primary consensus in 2012—the candidates have little interest in explaining their personal theories of how the imaginary "anchor baby" crisis should be resolved.