Kentucky Secretary of State Trey Grayson has long been viewed as the hand-picked favorite of Senate Minority Leader and senior Kentucky Senator Mitch McConnell. But now McConnell is officially jumping into the race by directly endorsing Grayson over insurgent candidate Rand Paul in a new statewide television ad. This is a big late-game move by the Republican establishment to try to save its preferred candidate, Grayson, ahead of the May 18th primary.

Getting Kentucky Republicans to vote against Paul (son of U.S. Rep. Ron Paul, R-TX) looks like an incredibly steep challenge and one that even the most powerful Republican in Washington might not be able to pull off. The latest PPP poll has Paul with a commanding 46-28 lead against Grayson. A SurveyUSA poll from last month also showed Paul with a 45-30 lead over Grayson.

It will be interesting to see if this big move by McConnell will pay off. If Paul wins in spite of the endorsement of the most important Republican in the country right now, it will be another sign of how powerful the insurgent anti-establishment forces have become in Republican politics. So far this cycle, one senator, Arlen Specter, and one governor, Charlie Crist, have left the party due to insurgent primary challengers. Another senator, Bob Bennett, is in serious danger of losing his party’s nomination, and even 2008 Republican presidential nominee John McCain is facing a legitimate primary challenger.

If the Senate Minority Leader is unable to affect who wins the GOP nomination in his home state, it would mean there has been a real shift of power from the party establishment to the grassroots.