Rarely have two U.S. presidential front-runners needed more from running mates than Hillary Clinton and Donald Trump.
The Democratic and Republican leaders in the 2016 White House race are unusually unpopular nationally, polls show, despite their success with voters in their party. Clinton has struggled to generate excitement about her candidacy and assuage concerns about her trustworthiness, while Trump fares badly among women and minorities in polls.
Assuming each gets their party's nomination, their weaknesses increase the importance of their vice presidential pick, who could potentially help them rally support in key demographics ahead of the Nov. 8 vote.