Mark Russell, a master of political satire who stood at a star-spangled piano and kept the cognoscenti in stitches for six decades with musical parodies and professorial tomfoolery that tweaked politicians and captured the silly side of Washington, died on Thursday at his home there. He was 90. The cause was prostate cancer, his wife, Alison Russell, said. With his deadpan solemnity, stars-and-stripes stage sets and fusty bow ties, Mr. Russell looked more like a senator than a comic. But as the capital merry-go-round spun its peccadilloes, scandals and ballyhooed promises, his jaunty baritone restored order with bipartisan japes and...