For years, the most effective line of attack against Democrats has been that they don't stand for anything. Kerry was portrayed as a flip-flopper while people said that even if they disagreed with Bush, at least they knew where he stood. Bill Clinton was attacked as following the polls rather than leading. Gore was perceived by many as a bland policy wonk without clear principles.
Obama needs to avoid following in the footsteps of previous Democratic candidates. Obama needs to articulate the principles that guide his decisions. Instead of focusing on the various policy proposals he may have, he should focus on the basis for those proposals. Instead of talking about the details of, for example, a social security lockbox, he should talk about why we he believes we need a social safety net.
I suggest that Obama focus on the theme of freedom/liberty. Americans will be freer if they know they can get health care no matter what and if their health dollars aren't going to the insurance company executives. Americans will be freer if our tax dollars aren't wasted on contractors in Iraq. Americans will be freer overall if we reduce the tax burden on the majority of Americans, even if we have to raise taxes on the wealthy. Americans will be freer if we allow gay marriage. Americans will be freer if we reduce the "Gridlock Economy" trend that the Republicans have accelerated. Americans will be freer if we reduce the Bush police state. Etc. Obama can then contrast his ideas of freedom with Republican authoritarianism--I think it will be a very effective frame.
Obama should work to get people to say, "I don't agree with everything Obama says, but at least I know where he stands," just like they said about Bush. Obama has a great opportunity this week to define himself and clarify what principles really matter to him. I just hope that next week people aren't still saying that all he stands for is a vague notion of hope.