The Cliché:  Terry Keenan column in Saturday's New York Post ("Markets should ignore S&P") concluded, "Like the debt-ceiling showdown that dominated the discussion last week, the S&P downgrade of US debt is a sideshow, a needless distraction from the greater problem." It was a phrase CNN correspondent Jeffrey Toobin had used on Friday night's Anderson Cooper 360 ("I think this is likely to be a big sideshow") but it seems like Keenan's column got more play: it was was picked up by RealClearPolitics and subsequently by other blogs, many of which used the headline, "S&P Downgrade Is a Sideshow." That headline seemed to catch on with others thinking about the fate of world markets over the weekend. On Monday, Reuters quoted a J.P. Morgan strategist who said, "investors view the S&P cut as a 'sideshow' and as further reason to reduce risk." The New York Times DealBook editor Andrew Ross Sorkin writes today, "But the downgrade is almost a sideshow compared with the real reason that stocks started falling Monday morning." His Times colleague Joe Nocera also writes today, "In the end, a downgrade from a ratings agency shouldn’t keep anyone up at night; it’s a sideshow."

Where it's from: "Sideshow" was first used in 1846 and popularized by P.T. Barnum as part of his traveling circus. It is quite literally an attraction to the side of the main acts at a carnival or circus. A "sideshow" - both unimportant and silly (if not freakish) -- becomes an easy metaphor for frivolous and inconsequential politics, and political observers have been taking advantage since the 19th century.

Why it's catching on: We assign this one to the same old lack of creative language that causes time-pressed bloggers and pundits to borrow from each other everyday. Clearly the widely repeated quote from New York Post stuck in peoples' minds and it quickly became the defining word in the media's narrative of the downgrade over the weekend. The media's overwhelming analysis was that the downgrade would be unimportant and people would probably still consider U.S. bonds a safe investment so pushing the downgrade to the "side" seemed apt.

Why else? But a "sideshow" by definition is not just peripheral, it is also silly (and sometimes female and bearded.) This too fits well with the media's narrative in the wake of the downgrade. "S&P is a bad joke" said The Washington Post's Jonathan Bernstein. "S&P’s report is a joke," agrees the Post's Ezra Klein. Circus imagery helps them convey this narrative that S&P is not only to the side, but also a circus act, not to be taken seriously.