In the 50 days since news consumers were told that a federal whistleblower was expressing his disapproval of a presidential phone call, CBS News has aired or published more than 100 stories on President Donald Trump and Ukraine. Counting stories from local affiliates, the number rises above 200. That’s according to the Dow Jones Factiva news archive.

But CBS hasn’t come close to the wall-to-wall coverage offered by rival ABC News. A Factiva search of ABC stories about Mr. Trump and Ukraine yields 687 results for the last 50...