Number one, we are led by a president who has done nothing but try to blur distinctions between the two parties since day one, all in an atrociously misplaced sense of bipartisanship. Assuming he's sincere about that. Which I don't. But he has succeeded beyond anyone's wildest dreams.
Voters showed that they hated Repukes in successive elections culminating in 2008. Why Obama wanted to be just like Republicans on so many issues is beyond me, but he sure as fuck reversed the trend. As many of us predicted at the time.
Five more reasons below.
Number two, the rest of the party leaders have prioritized fund-raising as if it is an end in itself, which maybe it is for the consultant class. Since they are raising it from the same people the Repukes are, they promise their paymasters they will only give core Democratic constituencies the absolute minimum. That minimum might be enough to keep them from switching sides. It is not enough to get them up off the couch and to the voting booths.
Number three, the only serious distinctions between the parties are on social issues. Trickle-down; drill, baby, drill; bonuses for bankers; infinite surveillance and endless war, for example, are core policies of Democratic leaders from the White House on down.
Number four, the leadership, from the White House on down, is timid and feckless (see number two). "Bold" and "audacious" are not in their vocabulary.
Number five, shitty marketing, which I mention in various comments elsewhere.
Number six, a refusal to take Repuke voter suppression efforts seriously and invest in getting Democratic constituencies registered and equipped with voter IDs. You can't let your opponents take millions of votes away and expect to win. But media consultants don't make money on getting people equipped with voter IDs.
We have a party whose leaders think a winning strategy is to raise as much money as possible, no matter whom they have to sell out, and shovel it over to their consultant cronies. That's it. That's actually how they think they can win. And then, when betrayed Democratic voters are not motivated to get to the polls by advertising campaigns that for all the selling out are still a fraction of the size of Repuke advertising campaigns, they blame not their selling out, not their failure to raise enough money, not their shitty marketing, no. They blame the voters.