Rudy Giuliani’s account of Donald Trump’s role in the payment to Stormy Daniels has collapsed into near-incoherence. In his latest interviews, the newly minted Trump lawyer has adopted a posture of impenetrable epistemological modesty — there’s nothing he knows about the case, or can possibly learn about it anytime soon. Giuliani retreated to this tack after directly contradicting the president’s denial of knowing anything about the hush money, and getting rebuked by Trump for being ill-informed and not yet up to speed. It shouldn’t be this complicated. Getting their story straight would be much easier if they adopted a simple,...