One problem with the Trump-Russia investigation is that the facts continue to be released in dribs and drabs. The unreleased House transcript of the testimony of James Baker, former general counsel of the Federal Bureau of Investigation, is Exhibit A for why it is so crucial for Americans to get full documentation, and soon.

Bits of the Baker transcript have leaked, including a few explosive lines about the FBI’s musings over removing President Trump via the 25th Amendment. But it’s his Oct. 3 and Oct. 18 interviews as a whole,...