[cnn-photo-caption image= http://i.cdn.turner.com/cnn/2008/images/06/03/sd.jpg caption=" A woman casts her ballot in Sioux Falls, South Dakota. "]
(CNN) - We've talked all season about Barack Obama's problem with those white working class voters, those blue collar voters. Is that problem persisting?
Yes, it is. South Dakota’s Democratic primary voters with no college degree voted as their peers in previous contests had: for Hillary Clinton over Obama, 60-40 percent. Meanwhile, well-educated, white collar voters continue to back the Illinois senator. Take a look at college graduates in the state: they voted for Obama, 53 to 47 percent.
The effort to win over these working-class voters is just beginning for Obama – and it looks like he has his work cut out for him.