Barack Obama might be well advised to curb his occasional impulse for telling tall tales, lest the Republicans seize the opportunity to paint him as Pinocchio.

They've proved themselves quite adept at undermining their opponents' credibility. Al Gore, of course, was Exhibit A. He had sought to pad his resume on a number of occasions - by boasting that he was a top speechwriter for Hubert Humphrey in 1968 (he wasn't), by claiming that he came under enemy fire in Vietnam (he didn't), by insisting that he fought the tobacco companies after his sister died of lung cancer (he didn't) - and the GOP wove those incidents (and a few others, plus some that the GOP concocted) into a broad narrative about how Gore was a serial fabulist who could not be trusted with the presidency.

Obama risks serving up the same kind of ammunition. He has already provided several examples. Earlier this week, for instance, he remarked about how he "had an uncle who was one of the, um, who was part of the first American troops to go into Auschwitz and liberate the concentration camp" - when, in fact, Auschwitz, in southern Poland, was liberated by the Soviets in January 1945, at a time when the American troops were 1000 miles away. Obama was apparently referring to a great-uncle on his mother's side who helped liberate Ohrdruf, a camp within the complex known as Buchenwald, in the German region known as Lower Saxony, three months later. So: a misidentified relative, wrong time frame, and wrong geography.

And speaking of the wrong time frame, here's what Obama said in Selma, Alabama back in March, when he was trying to voice his solidarity with the famous Selma march for civil rights: "If it hadn't been for Selma, I wouldn't be here." He was referring to his parents, who marched in that event. He further explained: "So they got together, and Barack Obama Jr. was born. So don't tell me I don't have a claim on Selma, Alabama." But, actually, he has no such claim. He was born in 1961. The Selma march was staged in 1965.

Another time-frame problem surfaced a few months ago, when Obama sought to voice his solidarity with the Kennedys. He declared that he owed his "very existence" to the famous family, because, in his telling, the Kennedys provided the student scholarship money that enabled his future dad to visit America in 1959 and thus meet his future mom. The only problem with that yarn, as it turned out, was that the Kennedys' involvement with the scholarship program, which involved the airlifting of Kenyan students, did not begin until 1960 at the earliest.

Obama fans might deem these incidents to be trivial, but Obama has also fiddled with facts while discussing the people's business. Back in January, he intimated that, as a senator, he led the charge for a new law that compels nuclear plants to disclose low-level radioactive leaks. He said, "(T)he only nuclear legislation that I've passed has been to make sure that the nuclear industry has to disclose whatever they emit anything that might be considered radioactive, and share that with local and state communities. I just did that last year." But, in reality, that legislation did not pass. It got out of committee, but it was killed by the full Senate.

It is hardly unusual, of course, for politicians to pound their chests without empirical justification. Ronald Reagan used to tell world leaders that he witnessed the liberation of the Nazi concentration camps when, in reality, he saw it only on celluloid. Bill Clinton claimed to have "vivid and painful memories of black churches being burned in my own state when I was a child," whereas, in truth, Arkansas historians have said that the total number of burned black churches was exactly zero. And then there is my own personal favorite: the late-'90s claim by New Jersey Democratic Senator Bob Torricelli about how the 1951 Kefauver probe of organized crime was the "first hearing of the Senate I ever witnessed" - which suggests that Torricelli must have possessed superhuman cognitive skills, given the fact that, when the Kefauver probe concluded, he was a mere five days old.

Politicians behave this way for a variety of reasons - to better bond with the audience of the moment, to correct for their own perceived insecurities - and Obama is probably no different in this regard. Indeed, there have been other incidents, including his claim that as a child he became fluent in the Indonesian language within six months (a boast that has been contradicted by his first-grade teacher.) If Obama persists in this fashion, he runs the real risk of being Gored during an autumn election season that might leave him little margin for error.