It all depends on the amount of hatred that boils up after the 2008 election. Obama did well early in 2008 because Edwards divided the union/labor vote in the Iowa caucuses. Now, if Edwards if forced out early, Clinton will likely sail through the primaries, the nomination and the presidency, given the economy. Let’s say Obama is VP. Will Trump be as adamant about the birther issue for a VP? The channeled hatred against Obama was racist. Would sexism against Clinton be less severe or worse? I think opponents would be digging up issues from the nineties and thus, their effectiveness would be weaker. In 2012, Romney is not attack-oriented, so I think Hillary wins.
The real question is 2016. Obama is the heir apparent to the nomination. Would Trump have the same level of motivation to come down as hard on his opponents? Would he even get the nomination?