Democratic White House contender Bernie Sanders put front-runner Hillary Clinton on the defensive at a debate on Sunday, criticizing her for accepting speaking fees from Wall Street investors and sparring with her over healthcare.Sanders highlighted his own rise in opinion polls and showed a new level of fight at the most contentious of the four debates in the race to find a Democratic presidential nominee. It was their last face-to-face encounter before Iowa's caucuses on February 1.Clinton, who leads in polls nationally but has seen Sanders gain in the early voting states of Iowa and New Hampshire, tried to raise questions repeatedly about the self-styled democratic socialist's positions on Wall Street reform, healthcare and gun control.
