The Democrats gained control of both Congress and the Presidency. They then pursued ineffective policies which didn't fix the economy. They increased deportations of Hispanics. They restricted abortion rights for women. They spat on gays repeatedly. They betrayed unions. They gutted civil rights, going even further than George W. Bush (who never said he had the right to assassinate Americans.) They saved bankers who then rewarded themselves with record bonuses and salaries while average American wages actually declined.
The base was demoralized, not because the Dems went too far left, but because they went too far right. The non-Democratic voters were angered because they elected Democrats to fix the goddamn economy and to not be George Bush, who they were sick of. Dems didn't do what they were elected to do.
That's why Dems are losing - because they demoralized their own base in a base election year, because they didn't fix the economy, and because they thought Americans wanted them to be George Bush, just a bit smarter.
This isn't a repudiation of liberalism or progressivism or socialism (Americans wouldn't recognize a socialist if he gave them real universal healthcare) it is a repudiation of a Democratic party which failed to fix the economy and which became identified with bailouts for the rich.
Anyone who doesn't understand this, is, forgive me, a complete idiot.