The gentleman on the left is Senator Sam Brownback, one of the contenders for the Republican nomination for next year's American Presidential elections. Senator Brownback is described as being on the right wing of the party: presumably he perceives President Bush to be some kind of leftish subversive intellectual.
Of course, Senator Brownback holds resolutely conservative views on such hot-button issues as gay marriage, abortion, immigration and blowing up Abroadistan. So it's unfortunate that the word 'Brownback' suggests to me one or more of the following:
a) A slang term for a variety of heroin. ("Sheesh man, that gelcap o' brownback laid me out for two days.")
b) A slang term for an illegal immigrant. ("The harbour police just intercepted a crate with two dozen brownbacks come to work as hookers.")
c) Something unimaginable for which gentlemen advertise their fondness by means of a complex code of handkerchiefs in the back pocket. Or non-consenting variant of the same. ("That dumbass on my landing got uppity over a meth deal, so I got six brothers to brownback him in the showers. Mofo couldn't sit down for a week.")
Sorry, I've been watching The Wire.