KEY POINTS:
John Edwards wears jeans on the stump. Mike Huckabee plays bass guitar with local bands before his speeches and all the main candidates have been accompanied by family or people close to them on the campaign trail.
Their aim is to win perhaps the oldest game in a US presidential race - to persuade voters to like them.
Candidates trumpet their voting records, their experience and their strong principles. But unless they pass a basic test of likability, their chances of making it all the way to the White House are slim.
"Image is extremely important. Issues always come in a dismal last," said St Louis University political science professor Ken Warren.
"Most Americans don't follow politics very closely. Most people don't really know where these candidates stand on these various issues except in a very general sense."
Before the primary elections that will determine who will represent the Democratic and Republican parties in the November 2008 contest for the presidency, all the candidates have tailored their personal narratives to woo specific constituencies.
In a scene repeated throughout the campaign, Republican Huckabee dropped into a restaurant in Columbia, South Carolina, on Saturday and conducted seemingly casual conversations with diners eating breakfast in the midst of a scrum of reporters.
In one measure of likability, a higher percentage of Democratic voters associated the terms "friendly" and "down to earth" with Senator Barack Obama than with Senator Hillary Clinton or former Senator Edwards, according to a Pew Research survey in September.
On the Republican side, former New York Mayor Rudy Giuliani scored higher for those traits than rivals Senator John McCain, former Massachusetts Governor Mitt Romney and Fred Thompson, the actor and former Senator, the survey found.
Other polls have shown that Clinton is more likely to polarise voters than other candidates and that people who dislike her are prone to hold that opinion strongly.
In one example, Lynn Kartchner, a gun shop owner in the ranching town of Douglas on the Arizona-Mexico border, said in an interview: "She's a horrible person just like her husband [former president Bill Clinton]."
But Michael Dimock of the Pew Centre feels a candidate's ability to seem friendly is not necessarily a decisive factor in swaying voters. McCain, for example, was perceived by many Republican voters as a strong leader. As a result he might not be harmed by a parallel perception that he was less friendly than other candidates, Dimock said.
The same poll that rated Clinton as less friendly than her rivals also rated her "tough" and "smart" to a majority of Democratic voters. Giuliani was also rated as "energetic" and "tough" to a large percentage of Republicans.
The possibility that Clinton could become the first woman president of the United States has a particular resonance for many women and older voters.
Obama has presented his life story as an asset. Huckabee's rise in recent polls is based in part on his conservative credentials but also on the sense that he is a humorous man who successfully battled a weight problem - a struggle many voters relate to.
Asked at the South Carolina restaurant which was easier, to run for president or to lose weight, he said: "They are both pretty tough. [But] losing weight is the only time that a politician actually tries to jettison something."
- Reuters
