A grassroots leftist movement wouldn't get the same ruling class bankrolling that the teafascists got, so sadly this is unlikely.
Basically this. Though you do occasionally find left-wing eccentrics among the very rich. In Texas, we had Bernie Rapoport, a somewhat eccentric Jewish financier who was a self-described socialist. But he mainly used his wealth to fund higher education and the arts; he gave relatively little money to political campaigns. If you're someone who believes wealthy people shouldn't use their wealth to tilt public laws and institutions in their favor, you're not going to flood political races with your money in an attempt to change the outcome. There was also J. R. Parten, a very liberal oilman who supported FDR and Lyndon Johnson; while his conservative peers like H. L. Hunt and Fred Koch helped build up a conservative infrastructure of think tanks and political organizations that persists to this day, Parten is more or less forgotten about.
