Two-thirds of Americans, and nearly half of Republicans, are more likely to vote for candidates who campaign on fighting global warming, according to a new national poll. The number of Americans who believe climate change is caused, at least in part, by human activities has grown from 72 percent in a 2011 Stanford University poll to 81 percent in the latest survey, conducted this month. The view is shared by 88 percent of Democrats, 83 percent of Independents and 71 percent of Republicans.