I don’t recall him ever telling an Obama joke. He told an occasional joke which featured Obama, but never one where the joke was pointed at him. I must have quit watching too soon.
In his later years, his monologue got quite trite and expected until his writers went on strike. He was funny until they came back.
You don’t recall him telling an Obama joke because he didn’t tell a lot of Obama jokes. That’s not to say he never told them but he tried, like Carson, to be an equal opportunity offender. In that regard, he was very different than Letterman who was under the Svengali influence of his left wing producer.
Post #45 ludicrously retells a joke that supposedly Leno told but which is actually a very badly worded reworking of a line from Woody Allen’s “Hannah and Her Sisters”. The line was said by Max Von Sydow in one of his few comic performances. The joke was written by Allen.
Do not expect freepers to know what they’re talking about most of the time.