MOST politicians lie. Most people over 50, as I know all too well, misremember things. So here is the one compelling mystery still unresolved about Hillary Clinton’s Bosnia fairy tale: Why did she keep repeating this whopper for nearly three months, well after it had been publicly debunked by journalists and eyewitnesses?

In January, after Senator Clinton first inserted the threat of “sniper fire” into her stump speech, Elizabeth Sullivan of The Cleveland Plain Dealer wrote that the story couldn’t be true because by the time of the first lady’s visit in March 1996, “the war was over.” Meredith Vieira asked Mrs. Clinton on the “Today” show why, if she was on the front lines, she took along a U.S.O. performer like Sinbad. Earlier this month, a week before Mrs. Clinton fatefully rearmed those snipers one time too many, Sinbad himself spoke up to The Washington Post: “I think the only ‘red phone’ moment was: Do we eat here or at the next place?”

Yet Mrs. Clinton was undeterred. She dismissed Sinbad as a “comedian” and recycled her fiction once more on St. Patrick’s Day. When Michael Dobbs fact-checked it for The Post last weekend and proclaimed it worthy of “four Pinocchios,” her campaign pushed back. The Clinton camp enforcer Howard Wolfson phoned in to “Morning Joe” on MSNBC Monday and truculently quoted a sheaf of news stories that he said supported her account. Only later that day, a full week after her speech, did he start to retreat, suggesting it was “possible” she “misspoke” in the “most recent instance” of her retelling of her excellent Bosnia adventure.

Since Mrs. Clinton had told a similar story in previous instances, this was misleading at best. It was also dishonest to characterize what she had done as misspeaking  or as a result of sleep deprivation, as the candidate herself would soon assert. The Bosnia anecdote was part of her prepared remarks, scripted and vetted with her staff. Not that it mattered anymore. The self-inflicted damage had been done. The debate about Barack Obama’s relationship with the Rev. Jeremiah Wright was almost smothered in the rubble of Mrs. Clinton’s Bosnian bridge too far.