Shelbyville Republican Ed Gallrein, left, takes a photo with President Donald Trump in the Oval Office. Gallrein is challenging Republican U.S. Rep. Thomas Massie in the May primary. (Photo provided by Gallrein campaign)In conversation the other day, a political operative wondered why President Trump bothered to endorse Sixth District U.S. Rep. Andy Barr in the May 19 Republican primary for the U.S. Senate, since Barr was headed for victory anyw…