Wisconsin Gov. Scott Walker will announce his presidential endorsement Tuesday morning during a Milwaukee radio show appearance, his political office said Monday.Mr. Walker signaled last week that he will endorse Texas Sen. Ted Cruz, though he has yet to make that news official. WTMJ radio host Charlie Sykes, on whose show Mr. Walker will appear, said he has not been told whom Mr. Walker will endorse.“You would think I would, but I don’t,” Mr. Sykes said Monday.Last week Mr. Walker made it clear that he would eventually back Mr. Cruz. He has long expressed his skepticism of Mr. Trump’s campaign...