Liz Cheney for Attorney General

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 the Navy, respectively—demonstrating that stalwart Republicans would cross political lines to support FDR’s policy of aiding European democracies under threat of Nazi invasion. Republican leaders were enraged. But before long, the two appointees helped forge bipartisan congressional support for the president and worked with him to lead the allied forces to victory.

FDR’s decision was bold, especially given that it came a few months before a hotly contested presidential election. If partisan sentiments had prevailed, he could have lost the White House. Yet he put country over party and won re-election in November 1940.

Mr. Biden faces a distinct but similar challenge today. He must unite the country against antidemocratic forces marshaled by Mr. Trump and his advisers. Like FDR, Mr. Biden knows there are highly respected and capable Republicans who believe deeply in American democracy and will support him in this battle.

If America must now enter the uncharted waters of prosecuting a former president, appointing a Republican as attorney general would provide the public with crucial assurance that the rule of law—not partisanship—is behind the charges. Under other circumstances, there would be no cause to replace

Merrick Garland,

who has a fine record of unbiased and measured enforcement of our laws. But these are not normal times.

As vice chairman of the Jan. 6 committee, Ms. Cheney has shed light on Mr. Trump’s bid to hold the White House illegitimately. She has upheld fair elections and the rule of law as tenets of American democracy—principles many Republicans seem to ignore.

A graduate of the University of Chicago Law School, Ms. Cheney has the skills necessary for a superb attorney general. As a critic of the Obama and Biden administrations, a former member of the House Republican leadership and the daughter of a former Republican vice president, she has the requisite GOP bona fides, too. It’s possible Ms. Cheney would decline the president’s offer. But that shouldn’t prevent him from asking—or from seeking other Republican candidates in her place.

Americans disaffected with the two major parties are seeking bold ideas to address the nation’s challenges. By appointing a Republican to his cabinet, Mr. Biden would show decisively that he isn’t mired in partisanship. Such a move would signal that he’s ready to reach across the aisle to protect the great American democratic experiment.

Mr. Shinkle is author of “Uniting America: How FDR and Henry Stimson Brought Democrats and Republicans Together to Win World War II,” forthcoming in October.