SurveyUSA shows that the Jeremiah Wright scandal has had a strong impact on the primary campaign, to the detriment of Barack Obama. Real Clear Politics looks at the damage done thus far, although the polling preceded Obama’s speech in defense of his relationship with Rev. Wright. The results may give Hillary Clinton some ammunition for her argument to superdelegates:

[Ohio:] For Obama, it’s a 17-point swing against him since the last SurveyUSA poll taken just three weeks ago, going up from up ten on McCain to down seven. Clinton has slipped four points over the same period but still leads McCain by six.

[Missouri:] Again, Obama’s support slipped three points in Missouri while McCain’s rose five, giving McCain a substantial 14-point lead. Over the same period Clinton picked up four points on McCain according to the SUSA survey.

[Kentucky:] Not that Kentucky was in any danger of going blue, but McCain’s support jumped 10 points and Obama’s dropped five in three weeks. Clinton’s support remained steady, though she trails McCain by 10.

Note that both McCain and Hillary have gained in the same period in which Obama dropped like a stone in these key states. Ohio’s results will make the strongest argument for Hillary. If the Democrats want to beat the Republicans in November, they need to flip Ohio while holding onto their other 2004 states. Against McCain that becomes especially important, because McCain can compete with them in Michigan and Pennsylvania, two states that John Kerry and Al Gore won against George Bush.

These polls will set the question up for the superdelegates. The next round of polling will show whether they need to make a decision to throw Obama over the side on an electability argument. If the polling continues to slide for Obama in Ohio and Missouri, and if McCain continues to do well in Michigan and Pennsylvania, the Democrats simply cannot afford to nominate Obama. That, in fact, is the express mission of the superdelegates — to avoid a general-election disaster like George McGovern, and not to simply rubber-stamp the popular vote or the pledged-delegate leader.

Will the superdelegates have the guts to make that call? You can bet they hope that Obama’s polling before Pennsylvania makes a dramatic improvement so that they don’t have that responsibility thrust onto them.