Washington ? Democrats Wesley Clark and John Kerry are basing their presidential campaigns largely on military service that includes combat in Vietnam — a distinctive qualification in a race full of candidates who came of age during the war but did not fight.

Their White House rivals did not serve in Vietnam, even though most turned 18 while young men were being drafted. They escaped combat with deferments for college, medical problems, fatherhood and by serving in the National Guard.

President Bush was the National Guard during the war and did not see combat.

Clark and Kerry mention their military service in nearly every campaign appearance, offering their credentials as evidence they are best prepared to lead the nation during the fight against terrorism.

Clark was an Army infantry officer and company commander in Vietnam. He rose to four-star general and supreme allied commander of NATO forces in Europe. Kerry was the skipper of a Navy swift boat in the Mekong Delta of South Vietnam.

Both men received the Purple Heart after being wounded in combat and were awarded the Silver Star for gallantry in action.

“Obviously we’ve had presidents who haven’t had military experience,” Kerry said in an interview. “I understand that. It’s not a prerequisite. But we are living in a very different time.”

Military service used to be almost a requirement for winning elective office. In 1977, nearly 80 percent of House members were veterans. Some 76 senators in 1983 were veterans. Today, just 28 percent of representatives and 35 senators have military experience.

Twenty-five of the 43 U.S. presidents have served in the military.

Presidential candidate Sen. John Kerry, D-Mass., is seen in this 1969 photo as a Navy lieutenant, center, with members of his crew aboard PCF-31 in the Mekong Delta during the Vietnam War. Kerry and Wesley Clark are the only Democratic presidential candidates who served in Vietnam.

A review of the presidential candidates’ Selective Service records shows that only Sen. John Edwards of North Carolina and Howard Dean were assigned a lottery number.

Edwards was assigned No. 178 for 1973, but the draft ended that year before his number was called.

Dean was assigned No. 143 for 1970 — a number that was called up — but he was rejected after a physical in February of that year. In an interview with the AP, Dean said he had known since he was in high school that he had an unfused vertebra, a condition called spondylolysis.

Dean tried to spell the condition during the interview, but got it wrong after three tries, even though he is a medical doctor and worked as an internist before entering politics.

Like Dean, anti-war candidate Dennis Kucinich was disqualified from serving because of a medical problem. The Ohio congressman said he had a heart murmur.

Sen. Joe Lieberman of Connecticut and Rep. Dick Gephardt of Missouri each initially got 2-S deferments for undergraduate studies and then law school. After graduation, Gephardt joined the Missouri Air National Guard as a legal affairs officer and got a 1-D classification that kept him from being sent to Vietnam. Lieberman got a 3-A deferment for becoming a father.

Candidate Al Sharpton turned 18 on Oct. 3, 1972, just as the draft was winding down.

Wesley Clark, left, who was an Army infantry officer and company commander during the Vietnam War, is seen in October 1969 at the Hai Khi, Vietnam Base Camp.