Barack Obama is a Muslim. He attended a Wahabi school that taught radical Islamic doctrine and trained terrorists in Jakarta. He swore into office as senator of Illinois with a Koran rather than the Bible. The church he and his family attend is for black people, and excludes whites.
None of these claims are true. They are smears that first began to circulate online via e-mails last year. But they circulated so widely that several newspapers checked out the school in Jakarta, and Mr Obama's campaign had to set up an anti-smear website to clarify the rumours.
The presidential hopeful is not the only victim of smear attacks, however. Republican vice-presidential nominee Sarah Palin is the latest target. Fake photographs of her in a bikini and making seductive gestures, as well as rumours of a secret lover - a tabloid newspaper reported that the former Miss Alaska runner-up had an extra-marital affair - have been doing the rounds online.
A smear does not have to be true to be effective. It simply needs to offer a fraction of truth - any weakness a political candidate might have - and elaborate and exaggerate it so that doubts are raised, throwing uncertainty into the hearts of voters.
There is nothing new to any of this. Smear campaigns aimed at damaging reputations have been a key strategy in every presidential election in US history.
But this year has been particularly vitriolic, and the culprit is the internet, which is the perfect medium for spreading damaging innuendos.
