Barak Obama has been on top of the world. His positions on specific issues haven't been widely publicized but it could be argued that all he had to do was continue with his optimistic and energetic vaguery and the nomination was in the bag. Now he has gone public with a specific position on a controversial issue and it just might be a deal killer.
Obama is going after the Hispanic vote with his declaration of support for drivers licenses for illegal immigrants. It's not a new position for him. He held the same belief when he was a state senator in Illinois. It's new to this campaign though, and it's a position about 2/3 of the American voting public strongly disagrees with him on. What's more it's the kind of issue that will make people vote against you, even if they support the rest of your program.
Obama argues that issuing licenses to illegals is a safety issue. The roads would be safer if these people were properly trained and insured. The public sees it as institutionalizing the neglect of our borders. Americans don't want to make illegals better drivers or "easier to track". They want them to get back in line and come here lawfully. The drivers license policy is seen as surrender and will not sell.
This is not good news for Republicans. Obama has charm and stage presence and charisma, but is very beatable on the issues. That's because he has convictions. He really believes in what he says he believes in. He can be challenged on the merits of his ideas. Hillary is grounded only in the firm belief that she should be president. You can't nail her down to a specific position because she'll change it when and if necessary. The Clintons run on emotion and remember, they don't have to manage emotion throughout the whole campaign. They just have to hit the right note on the right day. They are very aware of this and very good at it.