In comments he first introduced on the trail Thursday night, Obama chastised Clinton for trying to make an issue of the fact he admitted at a recent debate he is at times disorganized, and mocked both Clinton and John Edwards for what they offered as their "weaknesses."
"I said, 'Well, I don't hang on to paper really well. My desk is a mess, so you know I need people to help me filing and keeping on schedule and things like that,'" he told a raucous crowd in Las Vegas. "And so my two colleagues - Sen. Edwards says um, 'My biggest weakness is I'm just so passionate about poor people and helping them,' and then Hillary says, ‘My biggest weakness is I'm so impatient to bring about real change in America.'"
"Now, I didn't, nobody had clued me in, that ya know, see, if I had gone last I would have said 'My biggest weakness? I like to help old ladies across the street," Obama deadpanned to laughter.
"I didn't understand the question," he said, laughing. "But this is what I mean. This is political speak. This is what you learn in Washington from all those years of experience - it's funny, except its sad, because it means that the American people are constantly having to sort out ‘what do people really mean?’"
Obama also went after Clinton for saying in the recent debate she was pleased a bankruptcy bill she voted for in 2001 failed to become law, and suggested it fits into a larger pattern of the New York senator often not being upfront.
"She said she voted for it, uh, but she hoped that the bill would die," he said. "Anybody remember that? Think about that. She voted for it even though she hoped it wouldn't pass."
"I've been less worried about making political points on these things, but getting them right," Obama continued. "That's the kind of leadership that I intend to offer as President of the United States. Somebody who will be straight with you and get it right the first time."
Obama's tough talk is a departure from how the Illinois senator campaigned in Iowa - a state where voters are often turned off by negative campaigning - and in New Hampshire, where polls suggested he would easily cruise to victory. Recent polls out of Nevada suggest all three Democrats are in a tight battle for the top spot ahead of Saturday's caucus.
- CNN's Alexander Mooney and Chris Welch