The political landscape is littered with Democrats whose campaigns have been hurt by questions about their patriotism. Barack Obama wants to avoid the same fate.

Critics have questioned Obama's patriotism for months, whispering about why he didn't wear a flag pin on his lapel and contending he didn't put his hand over his heart during the Pledge of Allegiance. Republican rival John McCain has asserted that Obama has placed his political self-interest ahead of his country's.

"Behind all of these claims and positions by Sen. Obama lies the ambition to be president," McCain said this week during a speech at the Veterans of Foreign Wars convention.

From Abraham Lincoln to George W. Bush, the Republican Party long has put a premium on patriotism. But it's a quality that is often ill-defined. There's the patriotism of military service and national security, and the patriotism of believing the U.S. can live up to its ideals and be a better place.

"The Republicans have taken that first type of patriotism, that muscular, military, 'rockets' red glare' type of patriotism, and driven that as a wedge against people they see _ Democrats, liberals _ as weak on national security issues," said Leonard Steinhorn, a professor of politics and media at American University in Washington.

Michael Dukakis' 1988 presidential campaign often serves as a cautionary tale for Democrats. Republican George H.W. Bush turned the Pledge of Allegiance into a campaign issue, criticizing Dukakis for vetoing a bill, as Massachusetts governor, that would have required teachers to lead public school students in the pledge at the start of the school day. Dukakis said he supported the pledge but vetoed the bill because a state Supreme Court opinion said it was unconstitutional.

Another strategy has been to paint anti-war candidates as unpatriotic. Even decorated military veterans have fallen prey.

During the bitter 2002 Senate race in Georgia, Republicans questioned the patriotism of Democratic Sen. Max Cleland, a Vietnam veteran who lost both legs and an arm in the war. The GOP ran ads with pictures of Osama bin Laden and Saddam Hussein that blamed Cleland for hampering President Bush's plans for a Homeland Security Department. Cleland lost the election.

Still fresh in the minds of many Democrats is John Kerry's defeat in the 2004 presidential election. Like Cleland, Kerry served in Vietnam with distinction. He was attacked by the Republican-funded group Swift Boat Veterans for Truth. The group ran ads questioning Kerry's war record and criticizing his anti-war activities.

Navy records contradicted the Swift Boat charges, but doubts about Kerry's service hung over his campaign. Kerry has since said he should have taken greater steps to confront the allegations.

But playing the patriotism card doesn't guarantee a win.

The 1992 presidential campaign pitted incumbent President George H.W. Bush, a World War II naval aviator, against Bill Clinton, who avoided military service during Vietnam because he was studying overseas. Opponents tried to paint Clinton as a draft dodger who organized war protests.

In the post-Cold War era, and with the economy sinking, national security became less of an issue, a turn that helped Clinton defeat Bush.

Questioning a candidate's patriotism can work because it creates doubt, said David Gergen, a former adviser to presidents from both parties. That's what McCain is trying to do when he accuses Obama of being willing to lose the war to win the election, Gergen said.

"I think the patriotism question in this case is being wrapped into this larger issue that he's not one of us," Gergen said.

McCain first tapped into this theme in July, shortly after Obama visited Iraq. He's continued to criticize Obama for opposing Bush's troop buildup in Iraq, which has helped quell violence in the country, then refusing to acknowledge its success.

"Even in retrospect, he would choose the path of retreat and failure for America over the path of success and victory," McCain said Monday.

The McCain campaign insists they're not taking swipes at Obama's patriotism.

"This is about judgment," McCain spokesman Tucker Bounds said. "It showed that he'd put a campaign victory ahead of a military victory."

The Obama campaign has been proactive in responding to perceived criticism of Obama's patriotism, including launching a Web site dedicated to dispelling myths and rumors. It includes video of Obama reciting the pledge, hand over heart.

During his own appearance before the Veterans of Foreign Wars, he challenged McCain to stop questioning his patriotism.

"If we think that we can use the same partisan politics where we just challenge our opponent's patriotism to win an election, then the American people will lose," Obama said Tuesday.

Prominently displayed on Obama's lapel during the speech was an American flag pin, which he now wears consistently.