reagan's favorite joke

Back in the 80’s I remember that another politician gave President Reagan a painting that was an illustration of the punch line of what was supposed to be Reagan’s favorite joke. The punch line was “F*** you, and the horse you rode in on.” I have never been able to find the rest of the joke. Does anyone out there in the teeming millions have the answer to this one?

I don’t know if this is Reagan’s joke, but it fits the punch line.

A cowboy is looking for a fight. He’s told that a nearby town is the unfriendliest town in all the west. So he saddles up his horse and rides to the town, determined to fight with the unfriendliest person he sees.

As he rides down the main street, everyone flips him off; men, women, children. So he’s having a hard time deciding who’s the worst. Then he looks and sees one man is gesturing with both hands. The right hand has the traditional middle finger pointing up in the air; but his left hand is turned with the middle finger pointing sideways.

Having found his man, the cowboy rides up but before he starts fighting, asks the obvious question: “Why were you pointing your left hand sideways?”

“Because I was saying ‘Fuck you and the horse you rode in on.’”