I've seen Jeet make this point twice today but I don't think it's actually correct. As I understand it, the Sanders theory is that his agenda will mobilize a constituency of voters so large that it will actually realign the electoral dynamics that have led to Congressional gridlock. As the argument goes, Democrats have been unable to do this because they have been unwilling to advance an agenda as radical as his. By tracking left, Sanders hopes to mobilize America's huge population of non-voters and even, counterintuitively, a significant number of self-identified Republicans. With large enough coat-tails Sanders can reshape Congress, and with a large enough mandate he can cow the remaining opposition into self-interested negotiation.@CarlBeijer @jbouie I'd add that both Sanders & Clinton need to lay out a theory of change. Neither quite has one.— Jeet Heer (@HeerJeet) October 16, 2015
This is of course a fairly common perspective on the left, holding that the internecine war of partisan tribalism hides latent consensus centered on class interest. Any politican who can tap into that interest will necessarily mobilize an enormous constituency that Democrats have not been able to mobilize given their investment in the status quo.
Whether you buy this is another matter, but it's all pretty straightforward and familiar to the point of political cliche. FWIW I think that it's basically correct, though I have my doubts that Bernie's agenda is actually revolutionary enough to get the job done. In any case, one can dispute his theory of change, but one can hardly say that it doesn't even exist.