Milton Wolf, at center. (AP Photo/Charlie Riedel)

Milton Wolf, the tea party challenger who spent most of this year trying to unseat Sen. Pat Roberts (R-Kan.) has finally endorsed his primary opponent.

But if Roberts was looking for a ringing endorsement, this isn't it.

In a post on his Facebook page that caught the Roberts team by surprise, Wolf urges supporters to back Roberts because the Senate majority is on the line. Roberts is in a close race against independent challenger Greg Orman, who has not said which party he would caucus with if the majority comes down to him.

A Republican familiar with the campaign said Thursday that Wolf and Roberts had still not met or spoken since the end of the primary.

"Whatever your opinion of Pat Roberts, his re-election to the United States Senate may be the deciding factor that dethrones Harry Reid and elevates solid constitutional conservatives like Ted Cruz, Mike Lee and Rand Paul into positions of influence to save America from Barack Obama," wrote Wolf, whose campaign against the senator was very nasty.

Then he added another caveat: "Be assured that if Pat Roberts is to be re-elected, I will do everything in my power to hold his feet to the fire. And be assured that the fullness of the duplicity, dishonesty and abuse of power that has marked this election will be exposed."

Despite the less-than-eager tone Wolf struck, it's still good news for Roberts. He needs every Republican vote he can get. And Wolf has a small but loyal tea party following that could help put Roberts over the top.

In September, there were rumors that Wolf might endorse Orman. Once the press caught wind, Wolf quickly moved to quash the rumors.