What Beet says is pretty fair (although, as I pointed out, the trust plank is just a mildly reworded version of the 1892 plank, and Cleveland created the ICC); but in any case the Democrats were always associated, despite periodic deviations generally mirrored by the contemporary Republicans, with economic liberalism. This carried through until the FDR administration. I also pointed out that the Democrats have always been the cultural left, from the Jacksonians to today.
I'm not sure that the party of Clement Vallandingham could be considered left in any way. The absorption of the Populists seems like a pretty good place to me (although there were of course times after that where the Democratic candidate for President ran to the right of the Republican, and partisan ideological differentiation at lower levels is a very recent thing).
