Surprising, unexpected, shocking, and stunning. Those are the adjectives the press used to disguise the collective OMG reaction to Pennsylvania Senator Arlen Specter’s decision to switch his party affiliation from Republican to Democrat. To be sure, this is a big thing, but surprising, it ain’t.

More than a month ago, a column in the Philadelphia Inquirer suggested that Specter should switch sides to improve his chances in the 2010 election. And that’s not even the most recent indicator that experienced political reporters and observers really shouldn’t have been blindsided by Specter’s defection.

There are lots of reasons for Specter to defect. His numbers are dismal going into the election. The GOP is dragging too. Not to mentioned that the right has never been crazy about Specter: “I do not like Arlen Specter,” Jonah Goldberg wrote at the National Review two years ago; six years ago, the magazine named him “the worst Republican senator.” Plus, he voted for the stimulus bill. Plus, he’s close with Biden and Obama. These seem like pretty strong indicators of Specter’s affinity for the Democrats. And, given Obama’s star power and momentum, Specter’s decision to hitch his horse to the winning party seems like clear, calculated politics, which is hardly surprising for an experienced politician. Oh, and Specter started out as a Democrat in his youth.

Certainly a senator who switches sides makes news. But no political reporter worth his or her byline could have possibly been surprised that a politically vulnerable, center-leaning Republican like Specter might defect to the Democratic party, given the current political climate.

So reporters are being disingenuous when they develop convenient amnesia to play this story as a shocker, when it really isn’t. That frame insults readers’ intelligence, and makes those reporters seem ignorant. What’s more, in emphasizing the “surprise” of the move, reporters miss a chance to produce something that explains how and why it actually makes sense. For political observers, this news is big—and, yes, it’s exciting. But excitement and surprise aren’t the same thing.

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Katia Bachko is on staff at The New Yorker.