It has been 10 days since Democrats received the glorious news that Senate Judiciary Chairman Chuck Grassley would require Donald Trump Jr. and Paul Manafort to explain their meeting with Russian operators at Trump Tower last year. The left was salivating at the prospect of watching two Trump insiders being grilled about Russian “collusion” under the klieg lights.

Yet Democrats now have meekly and noiselessly retreated, agreeing to let both men speak to the committee in private. Why would they so suddenly be willing to let...