Democrats should not expect the path to the White House to be a cakewalk if Hillary Clinton faces Donald Trump in November, former New Mexico Gov. Bill Richardson said Friday. "We've got to be very careful because Trump has tapped into a negativity, a populism that is out there, and I think we have to work extra hard" to attract young voters and turn out the party's base, the 2008 Democratic presidential contender told CNBC's "Squawk Box." Clinton will be a strong candidate, he said, but she will have to overcome her party's shift far left of the American electorate....