The massive political network founded by the Koch brothers endorsed GOP presidential candidate Nikki Haley on Tuesday, giving her a potential boost in her increasingly competitive primary battle against Florida Gov. Ron DeSantis and front-runner Donald Trump. The network, Americans for Prosperity Action, could be a vehicle for bolstering Haley’s ground game in the months leading up to voting in Iowa and New Hampshire, where the former UN ambassador has been building her presence. The Koch network has already spent millions of dollars attacking Trump in the Republican primary battle, and this endorsement marks its decision on who would be...