The race to replace former U.S. Rep. Aaron Schock has shaped up as a classic Republican primary, pitting the son of a longtime Illinois congressman and Cabinet member against a conservative writer who has railed at what he sees as the “establishment” GOP hand-picking the disgraced lawmaker’s successor.Three Republicans and two Democrats will appear on Tuesday’s ballots, but most eyes have been on State Sen. Darin M. LaHood, the son of former Transportation Secretary Ray LaHood, and Michael Flynn …