President Donald Trump on Sunday dangled the prospect of renewing his tariff threat against Mexico if the U.S. ally doesn't cooperate on border issues, while some of his Democratic challengers for the White House said the last-minute deal to avert trade penalties was overblown. It included a commitment from Mexico, for instance, to deploy its new National Guard to its southern border with Guatemala. Mexico, however, had already intended to do that before Trump's latest threat and had made that clear to U.S. officials.