Ballotpedia says 8 Utah incumbents have lost during the 2012 cycle. That's followed by seven in both North Carolina and Texas.In 2010, just over 8% of incumbents facing a primary challenge lost. This year it's nearly double at 14.8%. Governing breaks down the reasons for the turnover.
What’s causing this major shift? Redistricting, the once-per-decade redrawing of geo-political boundaries, may have played a role, according to the study. Forty states are using different maps this year than they were in 2010, and in several new districts, incumbents were pitted against each other, meaning that one of them had to lose.
Additionally, some anti-incumbent sentiment from 2010 may have carried into 2012, according to the study. “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,” researcher Geoff Pallay wrote.