Obama's campaign is nothing but negativity against Romney.

Observes Toby Harnden, noting a corresponding crankiness in the crowds that come out to see him.

... Obama is on the defensive and knows the only way he can win re-election is by the narrowest of margins, by ‘slicing and dicing’ – his own pejorative term – and eking out a 51 to 49 per cent victory, crawling across the line to 270 electoral college votes.

Via Rush Limbaugh, who says

Let me ask you this, any of you paying attention to Obama at these campaign appearances: Have you heard him say what he wants to do the next four years?... Have you heard anything that would qualify as a second-term agenda?...

[H]is entire campaign consists of trying to scare everybody in his pathetic base of voters about what a bad guy Romney is. That's all he's got. His agenda is to try to get people to hate Mitt Romney....

There is nothing comparable in this year's campaign to what Obama was getting away with in 2008. That was lofty....

He's implicitly saying that we should stay the course, but I can see why he's not leaning on that message. He can't do the old hope-and-change message, because he's the status quo. Getting us excited about hope and change could only push us toward Romney (and Ryan).