Let’s give plausible accounts of the known facts, then explain why demands that Robert Mueller recuse himself from the Russia investigation may not be the fanciful partisan grandstanding you imagine.

Here’s a story consistent with what has been reported in the press—how reliably reported is uncertain. Democratic political opponents of Donald Trumpfinanced a British former spook who spread money among contacts in Russia, who in turn over drinks solicited stories from their supposedly “connected” sources in Moscow. If these...