May 20 (Bloomberg) -- Whether he's deflecting criticism over his health-care plan or mocking a tribute to the Woodstock music festival, Senator John McCain has a trump card: the Hanoi Hilton.

That's the nickname for the site where he spent 5 1/2 years as a prisoner of war in Vietnam, a past that McCain regularly recalls on the campaign trail to fend off policy attacks, score political points and give voters a glimpse of his sentimental side. He campaigns with squadrons of POWs and made a video to mark the 35th anniversary of his release from prison.

When Elizabeth Edwards, wife of former Senator John Edwards, rebuked McCain's medical-care proposal and noted that he'd always enjoyed government health benefits, McCain responded that he knows what it's like to get inadequate care -- ``from another government.'' During an October debate, while knocking a Hillary Clinton plan to help fund a museum celebrating Woodstock, McCain said he missed the 1969 festival because he was ``tied up at the time.'' Even his rivals applauded.

The McCain campaign brings up the war ``often enough to make sure it stays in people's minds, but not so much that it seems exploitative and crass,'' said Paul Waldman, co-author of ``Free Ride,'' a book that argues the press has treated the 71-year-old Arizona Republican gently.

No Guarantees

While military service often earns public accolades, it doesn't guarantee success in presidential politics.

In 2004, John Kerry, a decorated Vietnam veteran, lost to George W. Bush, who had enlisted in the National Guard to avoid the Vietnam War. Bush supporters raised questions about Kerry's heroic conduct that dominated the debate for weeks.

Four years earlier, Bush defeated another Vietnam veteran, Al Gore. In 1992, Bill Clinton, who evaded military service, beat out a field of Democratic contenders that included Bob Kerrey, a Medal of Honor winner. In his re-election campaign, Clinton defeated Bob Dole, a World War II hero.

McCain is aware of the limits of military heroism at the ballot box. Before the 2004 presidential race, he told Kerry that even heroes-turned-politicians need a compelling message.

McCain said former Ohio Senator John Glenn, a decorated Korean War pilot and the first American to orbit the Earth, failed in his 1984 bid for the Democratic presidential nomination even though he was ``a bigger hero than either one of us.''

``It'll get you an admission ticket,'' McCain warned Kerry. ``But then you have to have something to say.''

Reluctant to Talk

In the years after he returned from Vietnam in 1973, McCain wouldn't talk about his time as a prisoner of war. A Navy pilot, he was shot down during a bombing mission over Hanoi.

McCain discovered the political cachet of his POW experiences while running for a House seat in Arizona -- after living there for just two years.

At a candidates' forum, he dismissed accusations that he was a carpetbagger with a well-timed ad lib: ``The place I lived the longest in my life was Hanoi.''

The audience burst into applause, and ``the race was effectively over right then,'' McCain would write in ``Worth the Fighting For,'' a 2002 book about his political career.

Under fire as a senator for questionable dealings with an Arizona friend and supporter during the savings-and-loan scandal, McCain fumed: ``Even the Vietnamese didn't question my ethics.''

McCain also touted his POW years at the 1996 Republican National Convention while nominating Dole as the party's standard-bearer.

Not Holding Back

This time around, McCain and his strategists aren't holding back either. They've created posters and aired television advertisements showing him as prisoner, lying on his back, holding a cigarette.

One vignette that he tells elicits tears from audiences. It involves a now-deceased POW, Mike Christian, who wouldn't be deterred from sewing American flags out of rags, no matter how severely his captors beat him, so prisoners could recite the Pledge of Allegiance daily.

McCain also talks about a guard who covertly loosened the ropes around his arms at night; he was the one Vietnamese whom McCain had hoped to see again when he returned to the Southeast Asian nation as a congressman 11 years later.

Answering Critics

He referred to his POW days today in Miami in a response to questions from reporters about accusations from Democrats that he's changed his positions on Cuba over the years.

``My record is unchanged and consistent for 24 years,'' McCain said. ``A Cuban officer and enlisted men came to Hanoi and tortured my friends -- killed one of them. My position on Cuba has been exactly the same.''

``A big part of the campaign is about character, and the campaign sees they have in McCain a real contrast with Barack Obama on the issue of service and being prepared to be commander- in-chief on day one,'' said Scott Reed, a Republican strategist who managed Dole's presidential campaign. ``The POW references are a part of it.''

Mark Salter, McCain's longtime Senate chief of staff and adviser, said he sees nothing wrong with highlighting the candidate's POW experiences, including his refusal to be released ahead of prisoners who had been captured earlier.

``Every candidate has a narrative, a life story to tell,'' Salter said.

For McCain, touting his POW years ``is not necessarily a deal-closer,'' said Republican pollster Tony Fabrizio. But against Obama, he said, ``it puts a bright underline on a couple of key differences between the two men: experience and stature.''

To contact the reporter on this story: Edwin Chen in Washington at echen32@bloomberg.net.

Last Updated: May 20, 2008 15:51 EDT