At an event (public, private, a party, etc.) where someone speaks (small speech; gives a toast; etc.) and everyone in the audience applauds automatically--in a kiss-ass sort of way.
"Palm" refers to clapping with your hands / palms, and jockey is just a sarcastic way to refer to the audience who are applauding.
When Obama gave his speech, it was interrupted, every few seconds, by the applause from the Kool-Aid drinking crowd...to which Mike uttered, sarcastically: "What a bunch of palm jockeys."
That guy is such a palm jockey.