Now that Rep. Liz Cheney has lost her primary to a Trumpist Republican in Wyoming, it’s time for President Biden to consider appointing her to his cabinet. Political tensions have risen to new levels since the Federal Bureau of Investigation’s Aug. 8 search of Mar-a-Lago. Bringing a Republican into the administration would cool partisan temperatures and unite the country in support of the rule of law. President Franklin D. Roosevelt used this strategy when the U.S. divided sharply over how to respond to Hitler’s aggression. In June 1940, he appointed Henry Stimson and Frank Knox as secretaries of war and...