I really, really, really do not understand how it is that we live in a country where people believe that Obama is a liberal (the most liberal president evah!). It's very frustrating. Worse is that because the more-conservative-than-Richard-M-Nixon President Obama is the Democrat, there is next to zero chance that there will be a quality candidate for progressives and liberals to vote for...possibly in my lifetime!
Whether this is just some form of creeping ideals that results from triangulating started with Clinton or something else really doesn't matter. What matters is who gets represented and how well:
Lunatic (right) fringe, crazy, fact denying, science hating, gold worshiping zealots can vote for Republicans and be relatively well represented.
Conservatives, to right-of-center people to moderates to maybe--just barely--left of center people (Regan Democrats) can vote for Obama and Democrats and be very well represented.
Left of center to moderately progressive individuals, if they are fortunate enough to live in a small subset of locations in this country, can find a US Rep to vote for who will represent them well (not be very effective, mind you, but will at least try). But already, these people get nothing they want--more progressive taxation, renewable energy, less pollution, better social security/welfare programs, ...--and the smattering of locations is woefully insufficient to accommodate this group (which is at least as large as the one immediately preceding).
It really isn't worth going further to the left. The lunatic left fringe (which does exist) has less than zero power. They are actively mocked by Democrats.
I really think that this is one of the reasons that Republicans are far more effective in elections than Democrats. The people that Democrats need to get excited to go out and vote for them have zero reason to do so. We never have a place at the table even if Democrats win. Goldman Sachs, on the other hand, gets heard and "respected" no matter who is in charge.
So why vote for Dems? I guess because the GOP is insane. May work [again] this year, but if they keep disenfranchising their base, the Democratic party will find itself to be as much a dinosaur as the current GOP. Voting for the lesser of two evils is not as inspiring as voting for something good. Obama had that chance at being something good, something inspiring, and he blew it something awful.