Mann and Corrado have new work on this topic, here is a brief excerpt from the Brookings summary:
The evidence suggests that increasing the role of small donors would have little effect on partisan polarization in either direction because small donors tend to be highly polarized. Although Mann and Corrado note that a healthier mix would champion democratic ideals like civic participation and equality of voice.
Taking both points together, Mann and Corrado find that campaign finance reform is insufficient for depolarizing the parties and improving governing capacity. They argue forcefully that polarization emerges from a broader political and partisan problem. Ultimately, they assert that, “some break in the party wars is probably a prerequisite to any serious pushback to the broader deregulation of campaign finance now underway.”
I view campaign finance reform as in general an overrated idea on the Left.