The thing is, if we are talking "the lesser of two evils", then you usually end up going with the "Devil you know".
What we are seeing is the more people see of Mitt Romney, the less they like him.
That is certainly true.
Romney does nothing for me.
Unfortunately you get weaker opponents when a sitting President is seeking election. I mean...look at the idiots the Dems put up against Bush Jr.
Same here. A serious candidate will usually wait until a sitting President reaches the term limit before running.
That's partially true.
More to the point, though, is that sometimes those weak candidates can do well, if they strike a chord.
Remember, in 1992, everyone thought Bush-41 was a shoe in after having a 87% approval rating after the Gulf War. So Mario Cuomo and Al Gore stood down and let nobodies and has beens run. And the race was Paul Tsongas, Jerry Brown and an southern governor named Bill Clinton.
The rest, as they say, is history.