Sometime within the next week or so, Joe Biden will make the most important decision of his political career. If he is elected president in November, it could have momentous — or disastrous — consequences for the United States: his choice of running mate.

Should Biden be defeated, his pick will be irrelevant. But with many polls showing him with a widening lead over Donald Trump, the woman he selects will matter a great deal, not just for us but for the world, since that person will be well positioned to become his successor, either as his heir apparent or even sooner should his presidency be cut short by death or serious illness.

Most presidential running mates have been essentially ticket balancers, who at least in theory helped to secure one or another desired constituency. Some have done well but others have been embarrassing failures, or worse. But historically, it is important, even urgent, for Americans to remember that vice presidents can and repeatedly since the 19th century have had a significant effect on our democracy.

This year, the vice presidency must not be a gamble. Far too much is at stake — given the continuing pandemic and its, as yet, unknowable aftermath, our exceptionally fraught racial landscape, the country’s fracturing relations with its traditional allies, and its deepening international challenges from China and Russia.

Seven times in American history, vice presidents have been abruptly elevated to the White House by a president’s death in office. Three were relative non-entities: Millard Fillmore after Zachary Taylor’s death in 1850, Chester A. Arthur after James A. Garfield’s in 1881, and Calvin Coolidge after Warren G. Harding’s in 1921. Two more were destructive shocks to the political systems of their day: John Tyler (“Tippecanoe and Tylor Too”), who after William Henry Harrison’s death in 1841 turned sharply against the Whig Party that had elected him, and Andrew Johnson, who became Abraham Lincoln’s surprise running mate in 1864, and who after his assassination the following year became, in the judgment of most historians, the worst past president in our history. More than any other vice presidential choice gone awry, Johnson offers lamentable proof that the office’s occupant can matter a great deal indeed.

Lincoln Bowed to the Political Pressures of the Moment

Accepting Johnson as the vice-presidential nominee was the worst single decision that Lincoln ever made as president. Never a Republican — the 1864 ticket was officially labeled the “Union Party” in an effort to woo Democrats’ votes — Johnson quickly reverted to his roots in the Democratic Party, and spent the remaining three years of his term doing his best to thwart the Republican congressional majority’s efforts to reconstruct the South after the Civil War. In the name of “conciliation,” he speeded the restoration of control in the South to former Confederates, ignored the rising terrorist violence of the Ku Klux Klan, and spurned enlargement of the rights of former slaves. He set back the cause of Civil Rights by a century.

Had Lincoln stuck with his first vice president, Hannibal Hamlin of Maine, the history of Reconstruction would have been far different and our subsequent racial history probably far less savage. Barely remembered today, Hamlin was one of the country’s eminent political men in his time, deeply experienced in the ways of Washington, having served creditably in both the House of Representatives and the Senate. He was both respected, well-liked by his peers, and trusted as a well-known quantity within his party. For nearly four years, he had performed his duties as vice president with modesty and skill.

It was also said that he was Lincoln’s best assurance against assassination, since Southerners knew that if he was killed they would face something much worse: a staunch abolitionist who had long pushed the president forward on emancipation, and one of whose sons was among the first officers to volunteer to command a black regiment. No one doubted that he was fully qualified, and fully prepared, to step into the presidency if he had to.

Instead, Lincoln bowed to the political pressures of the moment and opted to placate the restive border states where the Republican Party was weak. He allowed the party to name Johnson, Tennessee’s wartime governor, a deep-dyed racist who within months of his accession to the presidency betrayed the trust of Republicans who had accepted him on the ticket, many of them with grave qualms from the start. Some historians believe that Lincoln passively left the choice of his running-mate to the party’s convention, but he could without a doubt have indicated with a single word that he wanted to keep Hamlin on the job.

Appealing as They May Be, It Is Difficult to Imagine Those With Little or No Experience

In the three remaining cases, Americans got more than they expected with the sudden accession of a vice president to the executive office: Theodore Roosevelt after William McKinley’s assassination in 1901, Harry Truman after FDR’s death in 1944, and Lyndon Johnson after John Kennedy’s murder in 1963. All three were nationally known figures, deeply experienced, and came into office with the trust of the country. Roosevelt and Johnson, in particular, were exceptionally dynamic and imaginative leaders who surpassed the presidents with whom they had been elected and left lasting political achievements, although in Johnson’s case Vietnam would ultimately taint his considerable domestic legacy.

It would be naive to suppose that political calculation would not play a role in Joe Biden’s vice-presidential selection. He has already promised to pick a woman, and the pressure to pick an African American is considerable. Several presumed candidates are young women with great potential but thin resumes.

Appealing as they may be, it is difficult to imagine those with little or no experience in national government, much less foreign affairs, stepping smoothly into the presidency at a moment’s notice and deftly wielding the reins of government, especially in this era hyper-partisanship on Capitol Hill. We shouldn’t assume, of course, that a vice president untried on the national stage would necessarily fail at the job. And no one can remotely imagine that Biden would select a running-mate as damaging as Johnson. But history offers a cautionary tale, and America cannot afford a learn-on-the-job president.

Regardless of whom Biden chooses, female or male, African-American, white or Latino, he owes it to Americans to select a running mate who is able to shoulder the immense power of the presidency. Americans will be best served by a modest Hannibal Hamlin, or a future Teddy Roosevelt, not an Andrew Johnson or a Millard Fillmore.

About the Author 

Fergus M. Bordewich is a historian. His most recent book is “Congress at War: How Republican Reformers Fought the Civil War, Defied Lincoln, Ended Slavery, and Remade America.” He wrote this for InsideSources.com.