We are past the point where Obama can win a referendum election, regardless of whether it is on him or the economy. The success of his campaign is contingent upon two things. First, when focusing on the narrow sliver of undecided voters, between 6 and 8 percent of the electorate, the Obama team must make its candidate the lesser of two evils. It has to make the prospect of a Mitt Romney presidency so unpalatable that about half of those undecided voters will begrudgingly vote for reelection. Polling focusing on the undecided voters reveals they are a deeply pessimistic and angry segment of the electorate and don’t particularly like either candidate (fitting, because they don’t tend to like politicians). But they show signs of being more conservative than not. One unpublished analysis gives Republicans a 10-point advantage on the generic congressional ballot test among those undecided about the presidential race. Close analysis of the numbers shows that Obama might have an edge with between a third and a quarter of the currently undecided bloc. That’s cutting things awfully close.
The second key is turnout. African-Americans look solid for Obama and very likely to vote in high numbers, but young and Latino voters’ turnout appears problematic. Obama’s recent announcement of a newly articulated Dream Act-light policy could help, but it is too soon to see any data showing measurable change. It is what many Latino voters wanted to see, though Obama did it less than five months before the election when it could have been done three years ago. After deportations had reached levels higher than those under George W. Bush, it could take a lot to drive up Latino turnout.
I would note that the two strategies overlap. Obama's coalition is made up of youth, women, blacks, Latinos, gays, unions and old people. All of his moves are about scaring these groups about Republicans as a way of motivating them to turnout. He scares young people about student loans, women about contraception and abortion, blacks about supposedly "racist" Republicans, Latinos about deportation, unions about an end to the gravy train, and old people about cuts to Medicare. Many of his tactics are straw men -- Republicans aren't that likely to oppress blacks or gays or Latinos or women in any meaningful way, but that doesn't keep Obama from raising the GOP up as boogeymen.
I would also note that there is third strategy at play... kick scandals like Fast and Furious past election day. Whether he'll be able to get away with it is another story.