Former Senator Fred Thompson of Tennessee quit the race for the Republican Party's presidential nomination Tuesday after a series of disappointing finishes in the early nominating contests.  Thompson's withdrawal comes as the remaining Republican contenders focus on Florida while the Democratic presidential hopefuls are preparing for Saturday's primary in South Carolina.  VOA National correspondent Jim Malone has more from Washington.

Thompson issued a written statement withdrawing his candidacy and said he hoped the country and his party had benefited from his campaign.

He came in third in Saturday's Republican primary in South Carolina, capping a string of poor finishes in the early primary and caucus states.

Thompson entered the Republican race to great fanfare last year and for a time was near the top of the national polls.  But the former senator was never able to build political momentum for his candidacy, despite being well known as an actor on television and in the movies.

Thompson did not immediately endorse any of his Republican rivals, who are now focused on the Florida primary on January 29.  

Senator John McCain is riding high after his victory in the South Carolina primary, but he faces a potentially strong challenge from former New York City Mayor Rudy Giuliani, who has decided to wage an all-out campaign in Florida.

Giuliani questions McCain's commitment to conservative principles like cutting taxes.

"John McCain sided with the Democrats and voted against the Bush tax cuts," he said.

Giuliani led the Republican race in national polls for much of last year.  But he did not seriously compete in the early primaries and caucuses this year, gambling that he could restart his campaign in Florida.

But McCain's recent victories in South Carolina and New Hampshire have helped him in the national polls and in some states like New York where Giuliani was thought to be almost unbeatable a few months ago.

"We are now running 10 to 15 points ahead of him in his home state, so I understand," he noted.

Former governors Mitt Romney of Massachusetts and Mike Huckabee of Arkansas are also in contention in Florida.

Meanwhile, in the Democratic race, Senators Hillary Clinton and Barack Obama are getting more aggressive with each other in the battle for the party's presidential nomination.

OBAMA:  "Wait, no, Hillary, you just spoke."

CLINTON:  "I did not say anything about Ronald Reagan."

The latest debate in South Carolina was the most contentious exchange yet among the top Democratic contenders, including Clinton, Obama and former senator John Edwards.

"Are there three people in this debate, not two?  This kind of squabbling, how many children is this going to get health care?" he asked.

Obama is counting on strong African-American support in Saturday's South Carolina primary to regain some momentum after Clinton victories in Nevada and New Hampshire.  He is ahead in the latest polls in South Carolina.

Obama is returning fire at both Hillary and Bill Clinton for questioning his opposition to the war in Iraq.

"President Clinton says that I was not opposed to the war from the start, or says it is a fairy tale that I opposed the war, that is simply not true," he said.

Hillary Clinton is trying to stay competitive in South Carolina, but is already looking ahead to the February 5 contests when more than 20 states hold presidential primaries or caucuses.

Clinton contends Obama has a pattern of avoiding difficult issues, beginning with his record as a state senator in Illinois.

"It is very difficult having a straight-up debate with you because you never take responsibility for any vote, and that has been a pattern," she said.

The state-by-state selection process for the party nominees will be finished by early June and the party candidates will be officially nominated at the national conventions in late August and early September.

The U.S. presidential election will held on November 4.