Thanks for that. As noble as I believe the aims, knowing that it's funding Demand Progress has saved me from making a donation I would have otherwise regretted.
At its core, absolutely nothing. In its execution, it's extremely partisan. I'm neither a Democrat nor a Republican, but I've found that, for me at least, I despise when either side slings mud on the other.
Demand Progress isn't quite so blatant, in that they "question" Democrats, or "suspect" that they might be wrong, but similar judgements of the Republicans are downright hateful.
I don't begrudge their right to engage in "my party's right and your party's wrong" sorts of politics, but I will make sure that none of my money gets spent in furtherance of it.