Say what you will about the Tea Party (and I have a lot to say about them, not much nice), but give them credit: they had an impact. They forced the Republican Party so far right that I can almost feel myself getting stupider every time my family discusses politics, which thankfully isn't often.
Any progressive counterpart to the Tea Party will not be as well funded as they are The Tea Party is a totally grassroots movement of regular, average, real Americans, and to beat that, any progressive counterpart will need to focus on lower level grassroots moves of their own. Don't expect to intimidate politicians with money. Instead, we would have to focus on education and public awareness. Which brings me to another weakness to be overcome.
It's often been pointed out that the Tea Party movement consists largely of older generations. That works well in their favor for the moment. Older people vote more, and they are more politically active. Other than voter apathy, the worst thing for democracy is the idea that the Wednesday after you vote, your civic responsibility is done. Not so. Hold leaders accountable. Change isn't easy. Voting isn't even the bare minimum that an individual can contribute.