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 Feb. 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. Sanders pushed back at every turn.
He said Clinton had accepted hundreds of thousands of dollars in speaking fees as a former secretary of state from Wall Street backers.
"I don't take money from big banks. I don't get personal speaking fees from Goldman Sachs," the U.S. senator from Vermont said, adding, "I have huge doubts when people receive money from Wall Street."
He referred to his rising poll numbers in saying he believed he could expand his number of supporters to include more African-American voters, noting that when his presidential campaign began, Clinton was 50 percentage points ahead of him in the polls.
"Guess what: In Iowa, New Hampshire, the race is (now) very, very close," he said.
Casting herself as a candidate who would embrace President Barack Obama's agenda and build on it, Clinton said Senator Sanders had voted to deregulate the financial market in 2000 in a way that led to the central causes of the financial collapse of 2008 that pitched the US economy into a deep recession.
Clinton tried to undercut Sanders' support among Democrats who voted for Obama.
"He's criticized President Obama for taking donations from Wall Street. And President Obama has led our country out of the Great Recession.
"Senator Sanders called him weak, disappointing, he even in 2011 publicly sought someone to run in a primary against President Obama," she said.
Healthcare spat
Clinton pounced on Sanders' "Medicare-for-all" plan that was announced just hours before the debate and came in response to Clinton's criticism of his previous record on healthcare over his career as a senator.
The former secretary of state, former US senator and wife of former President Bill Clinton said Sanders' healthcare plan would undermine Obama's signature Affordable Care Act at a time when Republican legislators were still trying to repeal and replace it.
"I have to say I'm not sure whether we're talking about the plan you introduced tonight or the plan you introduced nine times over 20 years," she told Sanders.
"But the fact is we have the Affordable Care Act. ... We have already seen 19 million Americans get insurance." Sanders said he wanted to build on the Obama law by making health insurance more affordable.
"Nobody is tearing this up," he said, referring to the program popularly known as Obamacare.
"We're moving forward." Clinton also accused Sanders of being weak on gun control. She welcomed his decision on Saturday night to back a bill in Congress rescinding portions of a law giving gunmakers immunity from lawsuits.
But she said Sanders' record showed a more lenient attitude toward the demands of the powerful National Rifle Association (NRA) gun lobby.
Sanders defended himself, saying he has a strong record on trying to prevent guns from getting into the wrong hands and standing up to the NRA.
Sanders has pulled into a statistical tie with Clinton in recent polls in Iowa, whose caucuses are the first contest in the race to pick a nominee for the November election.
He also leads Clinton in the next state to vote, Vermont neighbor New Hampshire, on Feb. 9, according to polls.
(Writing by Steve Holland and John Whitesides; Editing by Mary Milliken and Jonathan Oatis)
