It is pretty remarkable how poorly establishment Republican candidates have done in this cycle of Senate primaries. One GOP officeholder, Bob Bennett of Utah, directly lost his party’s nomination. Another sitting Senator, Arlen Specter, left the Republican Party because he was afraid he would lose his primary to Pat Toomey.

Both Gov. Charlie Crist in Florida and former Rep. Rob Simmons in Connecticut were establishment candidates who stopped seeking the party’s nod when it became clear they were likely to lose.

In Kentucky and Nevada, GOP recruits for the race Trey Grayson and Sue Lowden, respectively, both fell to insurgent candidates. Lack of support from the party establishment didn’t hurt the winners.

That makes six serious establishment candidates in important Senate races who have lost or dropped out of the party nominating process–17 percent of the 36 Senate races up in November. That percentage is even higher when you exclude some of the very blue seats where Republicans are unable to find a decent candidate, and a few of the deep red seats with conservative Republican incumbents. There are also several primaries left this cycle where an insurgent candidate might defeat the establishment choice.

Currently, establishment pick Jane Norton is trailing Tea Party insurgent Ken Buck by 10 points in the Colorado Republican Senate primary, according to a new Magellan poll. The GOP establishment candidate could also lose in the upcoming Senate primaries in New Hampshire, Arizona and Washington State.

So far, this cycle has been very good for anti-establishment candidates in Republican Senate primaries. Republican primary voters hate the way Democrats are running the federal government–but they’re also not pleased with the job their own party establishment is doing in Washington.