What has caused the Democratic Party to lurch so far left?

[Orser67]

I would say three reasons:

1)Economic. Basically what Angus said.

2)A lot of the conservative Democratic voters have left the party or died out.

3)Young people and first and second generation immigrants are less affected by the mass disillusionment with government that began in the 1960s, and which still affects the voting behavior of the Silent Generation and Baby Boomers.