The Left wants to know.
During the primaries they thought that they knew Obama. They had every reason to believe that is a hard-left progressive. He lists a communist as a mentor. In college he would only associate with socialists and feminists. He spent time as a community organizer and doing work for the far-left ACORN. He announced his entry into politics at the home of one the the 1960s biggest radicals.
As the primaries dragged on, Obama actually moved to the left. He and Hillary were in a bidding war for who hated free trade more. His solution to nearly everything is more government regulation. His first action when inaugurated would be to order a rapid retreat from Iraq.
Obama's supporters expected that he would continue to run as a progressive and use his personal charisma to convince the populace that it didn't matter. Obama would win in a landslide with long coat-tails. He would then lead a purge of the Blue-dog Democrats and start work on a new progressive era to match Franklin Roosevelt's.
Instead he is running from the center and the left is having a fit. Arianna Huffington herself wrote a plea to abandon the middle and move back to the left. KOS announced that he is not making a contribution to Obama's campaign, after all. Even Keith Olbermann devoted a special comment section to persuade Obama to switch positions (again) on the immunity portion of FISA. He didn't even back General Clark when Clark questioned McCain's qualifications to be president.
Obama isn't doing much to sooth them. He switched sides on the immunity portion of FISA. He is back to wearing flag pins. He announced that he will expand Bush's faith-based programs. It even came out that his motto, Change you can believe in, and his logo were invented by his campaign staff and he doesn't like them.
There are a few possibilities. One is that Obama still has a far-left core of beliefs but is covering them up until after he is elected. This is certainly possible. For all of his talk about doing away with partisanship, he has never compromised with the right.
Or Obama could be a business-as-usual Chicago politician who will say anything to get elected and who will triangulate his policies just as Bill Clinton did. As we find out more about Obama he keeps looking like just one more corrupt Chicago pol.
Or he might be a centrist who simply followed the party line until he got a chance for power of his own.
I've seen it pointed out that Obama has taken positions that many of his followers dislike. Rather than questioning him they tend to assume that he is lying and that his true beliefs match theirs. With the current angst over his move to the center, possibly many Obama supporters are beginning to wonder what he really believes?