Romney needed a great summer (ie, horrible for everyone else) to make in-roads. The undecideds in this race are too low to wait until the last few weeks. He needed to define himself early, but he spent that time sucking up to the extreme right-wing and now he's suffering the consequences.
It's not all Romney's fault though. The summer of Bain really defined Romney in a negative way. People were saying the Obama was desperate to use these attacks but the truth is that it was a stroke of genius. The Obama Campaign really knows what it's doing, just like in the 2008 primaries and general election.