Topeka ? A former campaign manager for Kansas Republican Jerry Moran is now publicly endorsing Moran’s main rival for the U.S. Senate.

But Moran’s campaign said Sunday the former staffer is disgruntled and called the letter a trick of the campaign for fellow Congressman Todd Tiahrt.

Paul Moore said Sunday that he’s backing Tiahrt for the GOP nomination, after coming to believe that Moran was not instinctively conservative. Moore was Moran’s campaign manager from February through mid-April.

Moore made his comments in an open letter to Republicans, which he provided to The Associated Press. He also sent it to Tiahrt’s campaign.