It's pretty clear that Obama does not want to be identified as a Democrat. Presidential campaigns don't just accidentally forget to mention their party affiliation. The decision would have been made at the very highest level, by Obama himself.
People who have watched Obama over the years will not be surprised that he is running alone. When he ran for the U.S. Senate from Illinois, Obama positioned himself as a candidate who was beyond partisan politics. He paid very little attention to most of the other candidates who were running in the same election, putting all his effort into getting himself elected. He didn't want to be encumbered by the positions his party had taken in the past or by politicians whom he might not agree with on all issues. He didn't share the rock-star attention he was drawing to himself, and he didn't share the enormous amounts of money or volunteers he amassed.
Obama followed the same plan when he first ran for President. He was elected with the help of Democratic voters and the Democratic Party, even though he did almost nothing to help the party succeed. As a result, he had no coattails, and his election left him with a Congress that did not have the strong Democratic majority he needed. Once he was president, he turned his back on one Democratic constituency after another, angering his base.
Now, Obama is once again running on the Democratic ticket, but without any indication that he feels any obligation to his own party or even sees a value in having a Democratic Party. It would have been easy for Obama to urge at the convention that everyone work hard for the entire Democratic ticket. Presidents usually do that. But he didn't. He drew all the attention to himself. He told us what he had done during his first term, and what he was going to do during his second, as if he was the entire government and not just the head of one branch. Although he told us that the Republican message that “you are on your own” is an un-American message, that is precisely the message he was sending to nearly every Democrat who is running for Congress, Senate, governor, mayor, or sheriff, and to every Democratic party volunteer and voter. He is running for President, and the rest of us are on our own.
Obama does not seem to realize that without more Democrats in Congress, his agenda is doomed. The Republicans who opposed his policies will be no more interested in them after the election than they were before, and if there aren't more Democrats to support his policies, they will go nowhere.
Obama is a smart man, but in his zeal to promote himself he seems not to have understood what he told the nation in his big speech Thursday night, that we are all in this together. Unless he figures that out very soon and helps other Democrats get elected, he will have no more success in governing the nation during his second term than he did in his first.