Well, now wait a second. Let's not be too tough. A swing constituency was convinced that the Democrats had more and better to offer, upon a number of limited propositions (as in 1932).
Republicans had become demonstrably corrupt, formless, and agendaless in the majority in Congress, so voters tried to improve their representation with the phony "moderate Democrats" that Rahm Emanuel recruited to run against weak GOP incumbents.
Republicans allowed themselves to be snookered yet again by the East Coast Yacht Club, who always arrange open primaries in the East as the early contests, giving non-conservative, East Coast candidates like Rudy and Mitt an edge.
Too, remember that Obama ran a "blank screen" campaign (Tom Daschle admitted it, even before the election), onto which voters were invited to project their own aspirations, even as Obama made very few promises in the general election campaign. (And then he went back on some of them.)
So let's not beat up the voters too badly. They had a lot of help, steering them toward the Obamarats.
LOL...so where exactly does the buck stop? Despite your arguments its the voters responsibility to become informed. Bottom line is the vast majority are too stupid, self absorbed, lazy to do anything like that. Sorry, but the problem is Us not Them (mostly).