WASHINGTON — President Donald Trump did not rule out the possibility of seeking a third term in the White House, which is prohibited by the Constitution under the 22nd Amendment, saying in an exclusive interview with NBC News that there were methods for doing so and clarifying that he was “not joking.” “A lot of people want me to do it,” Trump said in a Sunday-morning phone call with NBC News, referring to his allies. “But, I mean, I basically tell them we have a long way to go, you know, it’s very early in the administration.” “I’m focused on...