Tuesday was a bad day for Washington establishment candidates and a bad day for conservative Democrats. All three establishment favorites performed poorly in the May 18 elections.

The most powerful Washington Republican, Senate Minority Leader Mitch McConnell (R-KY), endorsed Trey Grayson for Senate. Despite being the home state Senator, McConnell’s endorsement carried little weight in Kentucky. Rand Paul completely crushed Grayson, 59 percent to 35 percent.

President Obama also fared badly as an endorser. Along with the President, the Democratic Senatorial Campaign Committee and Gov. Ed Rendell gave the nod to former Republican Arlen Specter in Pennsylvania. Joe Sestak still managed to defeat him by a healthy margin.

Incumbent conservative Democrat Sen. Blanche Lincoln of Arkansas also had a bad showing despite the strong backing of Obama and the DSCC. She has been forced into a runoff against Bill Halter. Halter came very close to winning a plurality of votes, and stands a very good chance of winning the runoff.

The three Senate candidates with strong backing from their national party leadership–Grayson, Specter and Lincoln–did poorly. It was a good night for insurgent candidates, who did better than the polls projected.

So far, 2010 is an unfavorable year for establishment candidates. Marco Rubio forced Florida Gov. Charlie Crist to leave the Republican Party. Bob Bennett (R-UT) lost his party’s nomination at the state party convention. Mike Oliverio defeated incumbent Rep. Allan Mollohan (D-WV) in the primary. We’ll see if this is a pattern in upcoming primaries.