'Something has to kick off': Trump said to be hitting 'major hurdles' to keeping promise

Donald Trump made a key campaign promise that's going to be difficult to keep, according to a report.

Trump has said multiple times he hopes to end the birthright citizenship feature of the U.S., which many say is supported by the Constitution. The rule allows children born in this country to be citizens, even if their parents aren't.

Most recently, Trump said in a NBC interview that he hoped to get rid of birthright citizenship via an executive order.

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