A weekly cross-posted diary (at the top leftie sites) in which people vote on the Democrats against whom they are most eager to fund primary challengers. A running tally is developed, over time, of the top targets, and a database of people willing to pledge cash to as-yet-undeclared challengers.

And every time a politician appears on the list (with X number of votes), or rises in the ranking, he or she gets an email (or dozens of them), explaining that because of such-and-such a vote, or statement, or whatever, $X has been pledged to a primary challenge.

Then, at the end of whatever set period, we take the top one or two or five or ten (depending on the number of pledges) of the targeted Dems, and we call in those pledges.

But funding a few primary challenges isn't the main point. Really this is about exerting a small-but-constant pressure on a large number of Dems. An online institutional program to try to keep Dems on notice, using one thing they all hate--well-funded primary challenges--as a threat.