Hillary Clinton regains lead over Donald Trump in national polling taken after the conclusion of the 2016 Democratic National Convention in Philadelphia.
U.S. Senator Ted Cruz (R-TX) leads Donald Trump in Iowa by five points according to one poll, and then trails the real estate magnate by 13 in another.
Shane Vander Hart looks in-depth at the most recent polling in Iowa to see what is behind the rise of Donald Trump and Ben Carson and who has lost the most.