Louisiana Gov. Jeff Landry wants to be a kingmaker. But his efforts to elevate Rep. Julia Letlow’s Senate campaign is irritating other Republicans in the state. The first-term GOP governor has become a central figure in President Donald Trump’s revenge tour, working to boost Letlow to take down Sen. Bill Cassidy (R-La.), who is viewed by MAGA supporters as insufficiently loyal to the president. Landry has publicly endorsed her and dispatched his…