When Hillary Clinton first ran for president in 2008, she was badly stung by a backhanded compliment from rival Barack Obama, who called her "likable enough" before going on to win the Democratic nomination and the White House.

Eight years later, with her party's nomination to succeed Obama formalized on Tuesday night, the question of her likability, trustworthiness and honesty still hangs over her bid to become America's first female president, this time in the Nov. 8 election against Republican Donald Trump.

The Democratic National Convention in Philadelphia this week is, in part, an effort to reintroduce her to American voters, more than half of whom view her unfavorably, according to Reuters/Ipsos polling.