Once Mike Johnson’s speakership was merely implausible. Now it looks incompetent. The rookie Republican leader – already struggling to wield a tiny‚ extreme and malfunctioning majority – suffered a spectacular embarrassment on Tuesday night in a failed vote to impeach Homeland Security Secretary Alejandro Mayorkas. The drama undermined what was already a questionable case for impeachment – more over policy disagreements than the constitutional standard of treason‚ bribery or...