Of all the interesting things to be said about Robin Williams, this is not one of them: The late comedian was a reliable Democrat. Over the years he donated tens of thousands of dollars to Democratic candidates—Nancy Pelosi, Barbara Boxer, Al Franken. His political commentary was always liberal, in the general sense that Hollywood is liberal. George W. Bush was stupid; John Ashcroft lost to a dead man; etc. There are good reasons why these routines are not making it into the tributes to Williams. They weren't offensive, just sort of rote, spiced up by Williams' fast-switching impressions.
And I don't see many references to Williams' most explicitly political film, the justly forgotten Man of the Year, a strange, commodifed fever dream of the Bush-era left. Filmed during the pre-surge backlash to the Iraq war, released shortly before the 2006 midterms that gave Democrats their first real electoral victory in a decade, the film starred Williams as Tom Dobbs, the host of a Daily Show lookalike who was so damn honest about politics that he was successfully goaded into running for president.* In this (pretty typical) scene, Dobbs totally #disrupts a presidential debate by making fun of the major-party candidates' corruption and riffing on alternative energy.
The film took a twist that was not implied by the trailer, and seems quaint in a way that "Jon Stewart as truth god" does not. (Even now, in 2014, next-day videos of The Daily Show and Last Week Tonight are guaranteed traffic-makers on liberal news sites.) Dobbs wins the election because the shady company that built America's new voting machines made them busted and rigged. The company, exposed by a whistleblower (Laura Linney), is called Delacroy; the company that mid-aughts liberals worried was stealing elections was Diebold. Man of the Year made back its budget, but failed to anticipate the liberal comedy and snark that, by focusing obsessively on facts and individual stories, would come to define the Obama years.
*Correction, Aug. 12, 2014: This post originally misidentified Robin Williams' character in Man of the Year, Tom Dobbs, as Bob Dobbs.