Supporters of special counsel Robert Mueller’s investigation of Russian interference in the 2016 presidential election fear that acting attorney general Matthew Whitaker will soon fire Mueller. President Donald Trump, who appointed Whitaker after forcing Jeff Sessions’ resignation on Nov. 7, has denied collusion between his campaign and the Russians, and has repeatedly characterized the Mueller investigation as a “witchhunt.” But a move by Whitaker — a Trump loyalist — to fire Mueller would surely prompt a constitutional crisis, particularly after a Democratic majority takes power in the House in January. Yet there is another, more insidious threat to the investigation: that Whitaker will curtail it without firing Mueller and that, because of a loophole in the special-counsel regulations, the public would not find out until far too late.