In the last decade the number of people who consider themselves members of a third party rather than Republican or Democrat has more than doubled, and the number who consider themselves neither Democrat or Republican has risen to 37%, 6% more than the number of adherents claimed by either mainstream party nationwide. These voters are a force which neither major party can afford to alienate. In certain key states the gap is even larger. Independents dominate many of the western states where no party registration is required, and even some of the old northeastern states which require registration by party have more than 50% who register as independents. Even the number of people who vote 'straight ticket' in elections where it is allowed is declining as loyalist blue hairs become too old to vote. People like choice, but they don't like the choices the major parties are offering them, especially the Democrats. Over a 20 year period polls on poilitical identity have shown a 15% decline in those who identify themselves as Democrats with Republican numbers staying roughly even.
With membership declining and out of power in all of the branches of government, you would think that it would be time for unity among Democrats, but instead they've gone into a frenzy of divisiveness and recriminations. The moderate Democratic Leadership Council which brought them their successes of the Clinton era has become a target for attacks as "right-wing collaborationists" by those who feel that it betrayed the leftist traditions of the party and cooperated too much with the Republicans. The problem is that the DLC achieved its successes by appealing to moderates, and their far-left counterparts within the party like the Progressive Democrats of America have nothing to offer the voters who left the party or any of the other independent voters who are uncomfortable with the politics of either extreme. The success of this attack is demonstrated in the Lamont victory and the increasingly hostile rhetoric directed at other prominent DLC members like Hillary Clinton.
The far left feels that moderates have betrayed their party and that it's time for them to take over and reform the party on more of a socialist model. They have a good point. The voters who've slipped away over the years got tired of a party which seemed to have no convictions and no direction. They New Left has been extraordinarily effective in imitating the techniques of the religious right, revitalizing and subverting the party at the same time. They pursue their agenda remorselessly, targeting candidates within their own party for destruction and organizing grassroots movements through the Internet. They are determined to dominate the party, even if their destructive purges leave them with a much smaller, politically marginalized party to control. They may be winning the war for ideological purity at the expense of ever being a meaningful national party again.