There were some other primary challenges to less-than progressive Democrats, such as IN-09, OH-06, WV-01, WV-03, and multiple challenges in predominantly African-American districts, but they were not made explicitly to the ideological or partisan left of the incumbent. I don’t think Colorado Senate qualifies in that category, either, but I could end up being proven wrong.
Some notes:
The median incumbent result from the twelve campaigns that have already occurred is 60% for the incumbent.
The similarity of results in Blue Dog districts across the nation–Iowa, Pennsylvania, North Carolina, Utah and California–is striking. With the exceptions of GA-12, where an Obama radio ad skewed a predominantly African-American district, and IL-03, where multiple challengers made the incumbent’s numbers look lower than they really were, there is a narrow range of 32%-41% for explicitly left-wing challenge to the incumbent Blue Dogs. So, for the first time, we have an estimate of the anti-Blue Dog, progressive base in Democratic primaries.
If this progressive base were to increase its share of the Democratic party by 15%, then all of these primary challenges would either have won, or at least been serious enough to make the incumbent fundamentally change his or her behavior in Congress. In other words, we need another 15% to take over the party and put the Blue Dogs out of business.
All of this is extremely useful in letting us know where we stand in our efforts to reform the Democratic Party. It certainly will not be easy to get the last 15% we need, but at least it feels like an achievable goal. It’s a helluva a lot more doable than left-wing third parties ever making any headway.