A substancial number of the 47% are the elderly, and these people participate in the voting process in numbers far greater than their percentage in the population. A great deal of these Sr. Citizens see America going the wrong way, and will vote for Romney; however there are also life-long Democrats, who will tow the party line.
For some, their intellectual capacity does not allow them to view their political leanings with any more seriousness than they give to a Sports Team. If you are a sports fanatic, it doesn't matter what season your team has had, what crimes various players have committed, how many children the coach has molested ... they are "your team" and you stick with them through thick and thin. Unfortunately, this mentality is predominate throughout the DNC - the DNC is "their team" and no matter what happens, no matter if Obama was nuking US cities at random - they will support the DNC with their dying breath.
There is also a disturbingly large cohort of the voters who worry overly about voting for the winner. It’s almost like betting on the Super Bowl; people want to pick the winner rather than vote for the person who best represents what the voter sees as ideal.