Nate Silver has a helpful new graphic up at his FiveThirtyEight blog (now officially relocated to the New York Times) illustrating the not-so-risky gamble Tea Party Express took in challenging Sen. Murkowski. Not only are she and Utah's Sen. Bennett (who lost his primary earlier this year to Tea Party candidate Mike Lee) two of the most centrist Republicans in the Senate, Silver explains, they hail from two of the most conservative states in the country:

Under certain circumstances, these dalliances with centrism might be something Republicans might tolerate. It is unlikely that a senator significantly more conservative than Ms. Collins or Ms. Snowe could be elected out of Maine; instead, the seat would probably default to a Democrat. But Ms. Murkowski and Mr. Bennett hail from Alaska and Utah, two of the most conservative states in the country (although Alaska is somewhat idiosyncratically so), and Republicans could afford to be picky.

The graphic below plots Republican senators by how conservative their states are (the x axis) to how conservative their voting records are (the y axis). The dotted line represents how conservative one would expect the senators to be relative to their states' partisan breakdowns. Senators below the line are more liberal relative to their states.
 
  

nate silver murkowski graphic.png

Read the full story at the New York Times' FiveThirtyEight blog.