In the debates, the personal attacks are easily deflected ("there you go again" and Gore's sighing and crowding Bush), while the "are you better off now than 4 years ago" question hits home.
I think it's really easy to make the case we've seen almost 4 years of failed policies and easy to defend the retort that Romney's plan is going back to Bush policies. Romney isn't Bush, his economic plans are not Bush's, and we haven't seen what he can do as president. It's all scare tactics and trivial to point out they are.
Obama would be bucking the odds on many fronts.
The unemployment rate is higher than for any president reelected in recent times.
Few Democrats actually win reelection - since 1900, only Clinton, FDR, and Woodrow Wilson were reelected and two of those (Wilson & Clinton) won both times with less than 50% of the popular vote. Oddly, since some people claim people vote against their own interests, all republican presidents since 1950 have been reelected, except for GHW Bush (Ike, Nixon, Reagan, W).
Obama's signature achievement is an unpopular health care plan. Not only did the people revolt against this kind of agenda by electing republicans to control the house and a huge swing in the senate, too, but they similarly punished Clinton in 1994 for an equally unpopular (but failed) program.
Obama is not polling above 50% in the national polls. This is not good news for any incumbent.
Democrats just aren't as enthusiastic this time around about voting, at all, as republicans. The opinion polls don't matter if your side stays home.
