If it had seemed like anti-incumbency fever reached its pitch in 2010, take another look at the sleeper phenomenon taking over the 2012 primary races. Ballotpedia.org reports that, so far, a total of 135 incumbents have been defeated in the state legislative elections alone. This is an astounding number of defeats–nearly double the rate of incumbency defeats in 2012.

Bob Weeks reports from Kansas, which just held its primary on Tuesday, where 18 incumbents were defeated:

But yesterday, Kansas voters said goodbye to many of the left-wing Republicans — the so-called “moderates” or “traditional Republicans” — and nominated conservatives in their place. Some nominees face Democratic challengers in November.

The results are a surprise not only for the number of victories by conservatives, but the margin of victory.

It’s not just affecting Republicans; 44 of the 135 defeated incumbents were in Democratic primaries.

A report by Ballotpedia.org’s Geoff Pallay analyzes the phenomenon and how it compares to 2012 in a report available on Ballotpedia.org:

While the percentage of incumbents defeated in primaries in 2012 might seem low, the increase is nonetheless impressive. Redistricting may have played a role; in the 2012 primaries, 40 of the 44 states are using maps different from those used in 2010. A number of these redistricting efforts were challenged in the courts, and some were thrown out as the primary elections drew near. While redistricting is usually assumed to make it more difficult for incumbents to be re-elected, the unsettled nature of district boundaries also meant that all candidates were scrambling to adjust to these new district boundaries and re-arranging their campaign strategies accordingly.

Such developments made challenging an incumbent in a primary election even more difficult than it was in 2010, when redistricting did not take place. The costs of campaigns may have been driven higher, and candidates taking on entrenched officeholders historically have found it difficult to raise money.

Finally, it is significant that a pronounced “anti-incumbent” sentiment already existed in 2010, which benefitted challengers no less than it did in 2012. A possible explanation for the higher victory rate for challengers is that the higher win rate for challengers in the 2010 general elections triggered more aggressive challenges this cycle. Emboldened by the results of 2010, stronger candidates may have come forward to challenge incumbents in 2012.

With both Democratic and Republican incumbents losing at a higher rate than 2010, it shows Americans on both sides of the aisle are fighting back against an entrenched political establishment.