Gov. Chris Christie, who has long avoided wading into the immigration debate, said Thursday in Mexico City that he won't lay out his position on immigration reform unless he decides to run for president. "Until that time I have no role in the immigration debate, except for how it may affect the individual citizens of New Jersey, which I'll deal with as governor," the New Jersey Republican told reporters. "But I won't have anything to say on immigration unless and until I become a candidate for president of the United States," he continued. "If that happens, then I will articulate...