The White House looks set to release the House Intelligence Committee memo on 2016 government surveillance abuses, which means the attacks on the document by Democrats, the Federal Bureau of Investigation and the media are going to get wilder. To help navigate through the spin, here’s a handy guide for what to look for, and what to ignore:

• Rationale. Did the FBI have cause to open a full-blown counterintelligence probe into an active presidential campaign? That’s a breathtakingly consequential and unprecedented action and...