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In a roundtable discussion yesterday on ABC News’s “This Week,” ABC’s chief White House correspondent, Jonathan Karl, wanted to talk Senate politics. He showed a screen of polling numbers — President Obama’s very bad approval ratings in Montana (36 percent), Michigan (38 percent), Alaska (31 percent), Arkansas (31 percent) and Louisiana (40 percent). Karl turned to former White House senior adviser David Plouffe and asked:

Look at all these Democrats that are up in these tough, close races right now. There’s a new series of polls in several of these states. Look at Obama’s approval rating in the races where the battle over the Senate will be waged. Look, look how many states he’s below 40 percent. Don’t Democrats have a reason to maybe not be wedding their beds but being nervous about this?

That “new series of polls”? It came from conservative super PAC American Crossroads. The small print on the screen made that clear, though even an above-average viewer could have missed the attribution. Heather Riley, a spokeswoman with ABC News, tells the Erik Wemple Blog, “Upon further reflection, we should have given our viewers more context of where the poll came from.”

How massively did the American Crossroads-commissioned poll distort things? Have a look: That 36 percent Montana approval rating from American Crossroads compares with an, um, 29 percent approval rating based on an October poll from Montana State University-Billings. That 31 percent Arkansas approval rating compares to a 29 percent approval rating based on an October poll by the University of Arkansas. That 38 percent Michigan approval rating from American Crossroads compares with a 47 percent approval rating in a December poll by PPP. That 40 percent Louisiana approval rating from American Crossroads compares with a 41 percent approval rating in an August poll by PPP.

The numbers that Karl posted on the map, in other words, weren’t massively out of whack with other measures of the president’s standing in some key states. Plouffe didn’t challenge the numbers but rather flocked to other talking points. “The Republican brand is tarnished,” he said as part of his defense.

The story here is that fresh data makes news, even when the source has a huge stake in the outcomes. The American Crossroads numbers are based on a survey conducted by Harper Polling from Jan. 20-22, which is much more recent than the alternatives cited above. The Harper numbers were recently cited by the Huffington Post for under-representing Detroit and New Orleans. (Gallup also recently released state-by-state approval numbers based on interviews throughout 2013.) And yes, ABC News needs to scream the origins of the numbers. Because even if the snapshot approval ratings may have some merit, polling succumbs to biases.

“In the long run, polls that are sponsored by Democrats tend to miss in the Democratic direction,” says Scott Clement, polling analyst for The Washington Post. “And polls that are sponsored by Republicans tend to miss in the Republican direction.”

Erik Wemple writes the Erik Wemple blog, where he reports and opines on media organizations of all sorts.