DAY IN A NUTSHELL
Barack Obama and Hillary Clinton rip into each other's records during a televised debate in South Carolina, five days before the state's Democratic primary. Mr Obama attacks Mrs Clinton for having worked as a corporate lawyer and sat on the board of Wal-Mart. She hits back by describing one of his former legal clients and financial contributors as a "slum landlord". In Florida, two Republican candidates - Mitt Romney and Rudy Giuliani - air Spanish-language campaign adverts.
"It is Republican nature to abhor a Democrat-like free-for-all and to seek an anointed candidate. McCain is far closer to such status than is his principal rival, Mitt Romney."
Robert Novak, Chicago Sun-Times
"Mitt Romney is a family man, a great father, husband and grandfather. I know because Mitt Romney is my dad."
Craig Romney, in a Spanish-language campaign advert
"The former president, who I think all of us have a lot of regard for, has taken his advocacy on behalf of his wife to a level that I think is pretty troubling. He continues to make statements that aren't supported by the facts."
Barack Obama, on Bill Clinton
"We have passionate supporters, first and foremost [Bill Clinton], who makes a strong case for her candidacy. That's the way the process is supposed to work. Everything the president has said is factual."
Howard Woolfson, campaign spokesman for Hillary Clinton
Four polls published today all suggest that Rudy Giuliani's campaign strategy - ignoring the early primaries and relying on his strong national lead to win larger states like Florida and New York - may not be succeeding.
A Rasmussen poll of voters throughout the US has him in joint fourth place on 10%, 15 points behind the front-runner, John McCain on 25%.
Mr Giuliani also trails in Florida, a Rasmussen poll suggests, with 19%, to Mr McCain's 20% and Mitt Romney's 25%.
But perhaps the most worrying polls for Mr Giuliani are two surveys of likely voters in his home state of New York.
A Siena College poll puts him on 24%, 12 points behind Mr McCain on 36%, while a WNBC/Marist poll has him on 19%, trailing 15 points behind Mr McCain on 34%
Before the debate, the three main Democratic candidates put aside their differences at a rally in Columbia, to mark Martin Luther King Day