It happened because he took over and had to deal with Bush's mess. The economy was going downhill when he took office and he has managed to stall it while the economy gets better slowly and steadily.
To blame someone for the mess that they didn't cause in the first place is wrong, and you know it.
That might have been valid 3 years ago. But after 3 years with unprecedented access to government the Democrats really can't blame Bush anymore.
The problem is not Bush's recession. The problem is Obama's recovery. This is the weakest recovery on record, and appears to be close to an end anyway.
Obama's policies have produced records: lowest growth out of a recession, highest unemployment, lowest work force participation, highest decline in household income, highest decline in household wealth, etc. Why anyone thinks this man deserves a second term is beyond me.
The economy doesn't simply turn around in 3 years.
This is a capitalist economy, you know. You can't control where our money goes when there is constant outsourcing, price gouging, hoarding, etc.
Bush Era tax cuts have still yet to expire, which means a Bigger deficit (up to almost 1 Trillion)
Despite corporations having tax cuts, they are hiring less, laying people off anyway, and all of the higher up positions keep making their paychecks bigger and bigger at the expense of everyone else.
Small businesses keep going under while big business chains keep getting bigger.
Tuition prices keep going UP, UP, UP when college is still shitty and gets you NOWHERE do to the oversaturated job market.
The US doesn't try to import wealth through immigration (wealthy immigrants who WANT to come to the US)
Political corruption and lobbying
etc.
Just look at Romney's main contributors. They are all corporations who helped cause this mess. They see him as an investment for their benefit of putting more $$$ into their pockets, and have no problem screwing the majority over just to get what they want through illegal means.