John McCain has never stopped fighting.

From his boxing days at the Naval Academy, to his resistance to torture as a POW for five and a half years at Hanoi Hilton to his bid for presidency against tough Democratic incumbents, the 71-year-old keeps kicking.

"You size him up fairly quickly," said Orson Swindle of first meeting John McCain in Hanoi Hilton. "He's a fighter and one of the toughest I've ever known."

Sen. McCain (R-Ariz.) can no longer move his hands above his shoulders due to his brutal treatment as a POW.

Friends and co-workers report his stamina and tenacity are expressive of his character.

"He will never give up, he's tireless" said Bruce Merrill, pollster and director of the Center for Media Research at Arizona State University. "I've been involved in well over 100 campaigns for governors and representatives, and he's by far the hardest working and most determined politician I've ever seen in my life."

McCain's long family line of military leaders has impressed McCain with a strong sense of duty, said his college roommate Frank Gamboa.

His father was commander-in-chief of Pacific forces during the Vietnam War, his grandfather was commander of a carrier fleet against Japan in World War II and one of his ancestors served as part of George Washington's staff.

"He is very proud of his family and his family's heritage," Gamboa said. "He has a strong sense of history and always read a lot of history books."

After attending Episcopal High School, Alexandria, VA.,17-year-old McCain entered the Naval Academy, hoping to join as the fourth generation of naval grads, Gamboa said.

As his roommate for two years, Gamboa said McCain was one of the main personalities of their social group.

"He was very social, very intelligent and a very engaging person," Gamboa said. "He had a lot of natural leadership abilities and political skills."

Nicknamed "Silverfox" and "John Wayne McCain," because of his prematurely gray hair, Gamboa said McCain was very popular with girls and dated a lot.

McCain used to invite friends to his father's house in Washington D.C. on weekends for parties, Gamboa said. His sarcastic sense of humor provided a constant source of entertainment.

"His sarcasm is good-natured," Gamboa said. "He's very witty and loves a good laugh."

The roommates were boxers and wrestlers in college, but never played varsity because "we weren't that good," he said.

McCain exhibited a fervent interest in history, Gamboa said. His favorite movie was !Viva Zapata! A Mexican Revolution flick starring Marlon Brando.

While an avid reader, McCain did not particularly excel in class. He finished fifth from the bottom out of 899 students in the 1958 class, Gamboa said.

Yet McCain continued to fight.

When he was deployed to Vietnam in 1967, he survived a fiery crash on the USS Forrestal that killed 134 men.

Later flying over North Vietnam on his 23rd bombing mission, McCain's plane was shot down.

He was badly wounded when his aircraft hit, said Swindle. His leg, shoulder and lower forearm were broken. When the Vietnamese captured him, they smashed his other shoulder with a rifle.

The Vietnamese later left McCain in a prison cell with George Day, a fellow POW and Medal of Honor recipient, who was the first American McCain had seen.

Day doubted McCain would survive when he saw his "feverishly bright eyes," common before one dies.

"I never expected him to make it through the night," Day said. "I was positive he wouldn't live."

Again, McCain kept going.

For the next five and half years, McCain and about 600 other POW's survived extensive torture and interrogations.

"The whole episode from his case over five years to the longest held of nine years was a cycle of harshness, isolation, malnutrition, abuse and constant efforts to indoctrinate us with their propaganda," Swindle said.

When McCain was on the verge of dying, the Vietnamese offered John the chance to go home early, but he refused. McCain adhered to the rule of letting POW's who had been there longer leave first.

"John McCain has a keen sense of obligation and duty and honor and he knew to accept early release would be used in a ruinous fashion against his father, his country and his fellow POW's," Swindle said.

To pass the hours of boredom away, Day said he and McCain would spend hours talking about politics, work, women, drinking, flying, philosophy, history and everything else.

"We were both just a couple of cripples trying to live and recover," Day said.

Day said McCain emerged as a leader and source of entertainment for the group. He would recount movies he had seen to other POW's, Day said.

"I had a lot of really smart guys, all college grads, all fighter pilots, all pretty classy bunch of people, and John was a standout among some very talented in the group," Day said.

Although the POW's were mainly in isolation, McCain would often stand on Swindle's shoulders to reach high windows and flag other POW's. He would pass secret messages about resistance around the camp, Day said.

While at a naval hospital in Jacksonville, Fla., a nurse's report said McCain tried to hang himself twice while in camp to avoid giving in to interrogations.

After Day and McCain were both released on March 14th, 1973, McCain pursued his interest in politics. He and his first wife divorced shortly after, Gamboa said.

"He found in naturally interesting to him because of his feelings about the navy and government and service to America," Gamboa said.

McCain has served as senator of Arizona since 1982, his wife Cindy's home state. He lives in Phoenix with his seven children, one who they adopted from Bangladesh and two who just returned from Iraq.

Patrick Kenney, professor and chair of political science at Arizona State University, said McCain is generally well liked in Arizona but has never had any serious competition in the Senate race.

McCain has, however, faced opposition from right-wing conservatives of the Republican Party, who disagree with his stances on immigration, Kinney said.

Arizona district representative Rob Haney calls McCain a "dishonest flipflopper," mainly because of his changed stance on Bush's tax cuts and abortion.

Kinney said McCain will have trouble against Democratic incumbents because of his older age and longstanding presence in Washington.

"If change is one of the issues for the year, he certainly doesn't fit that," Kinney said.

With Mitt Romeny's endorsement and possible Mike Huckabee votes, Merrill said McCain has a strong chance in Arizona.

"I think McCain is a tough competitor, and he demonstrates and ability to bring Democrats and Republicans across party lines to support him," Merrill said.

McCain's fighting spirit seems to never stop.

"He's spent his entire life serving his country," Swindle said. "And it's the most important thing in the world to him."