Presidential contenders make closing arguments in Iowa

US Republican and Democratic candidates made last-gasp appeals to Iowa voters, with their White House aspirations on the line in the first nominating contest of the 2016 campaign. Republican Donald Trump and Democrat Hillary Clinton both were leading in the polls, but not by enough to assure victory for either candidate in Monday's caucuses. Will an establishment Republican -- Marco Rubio, perhaps -- outperform the polls and make it a three-way race with Trump and conservative Ted Cruz?