The cliché: The GOP primary race was all so flat and predictable, but then in August, it went on a wild ride. "Get ready for a roller-coaster ride in the up-and-down of Republican politics starting next week," National Journal's Matt Dowd wrote, predicting that the Iowa Ames Straw Poll results and Gov. Rick Perry's entrance into the race would send us to the amusement park (and not just because of the Iowa state fair corn dogs.) By all accounts, he was right. Just last week Bloomberg's Jeanne Cummings wrote "Republican voters' lack of enthusiasm for Romney has added to the roller-coaster nature of the primary." The Wall Street Journal's Gerald Seib reported on Monday, "Romney has held remarkably steady ... while others took wild rides up and down the popularity roller coaster." The Philadelphia Inquirer agrees that, "the roller-coaster pattern of the Republican race is interesting." 

Where it's from: Interesting, perhaps, but while the references didn't really get going until September of this year, historically, like a roller coaster, they tend to repeat themselves. Indeed "roller coasters" have popped up to describe nearly every recent presidential primary contest. "Strap on your seat belt, an Al Gore spokesman told Newsweek in March of 2000. "The roller-coaster ride has just begun."  "On the final hill of this roller-coaster campaign, Mr. Kerry has been relaxed and playful," The New York Times wrote in 2004. "Roller-coaster White House race heads south," declared ABC News in 2008.

Why its catching on: RealClearPolitics.com provides a convenient graph that averages the various primary poll results, and looking at it, one can immediately see why a roller coaster cliché might seem apt. The numbers for Rick Perry, Michele Bachmann, and Herman Cain have all moved up and down as would a theme park ride.

Why else? As candidate after candidate fails to sustain a lead over perennial 20-something percenter Mitt Romney, the news media is increasingly focusing on his inevitability, (arguing both for and against it.) A nomination that gets sealed up this far in advance of the primary contests would make for a boring few months of political news, but a roller coaster puts action into the contest, creating a sense that what goes up must come down. After all, what theme park would build a ride as boring as Mitt Romney's line on the tracking poll graphs? With many months until the convention, it's in the media's interest to, like a theme park, entertain and enthrall readers in the meantime. But forgive us if we feel like we've been on this ride before.