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The 2024 presidential election, like nearly all presidential elections, will be widely labeled the most important, momentous, existentially critical turning point in America's history. What's more certain is that the unfolding campaign really does have the makings of one of the nation's weirdest political spectacles.

That the Republican Party has ceased to be a functional political organization is clear from the apparent inability of its respectable elements even to put up a respectable fight against the renomination of Donald Trump. Twice impeached, four times indicted, seemingly likely to be on trial instead of on the campaign trail much of next year, facing legal efforts to bar him from the ballot as an insurrectionist — a politician lacking, shall we say, effortless likability — Trump would also be the second-oldest White House aspirant in U.S. history. An unusual choice for standard-bearer, to say the very least.

The oldest presidential nominee in American history, come 2024, would of course be Joe Biden, who shows his age (to say the very least). Bipartisan majorities of voters tell polls Biden is too old to seek another term. Surges of inflation and illegal immigration have soured the public mood. Challenges are in the works from third party candidates and are possible even from fellow Democrats (Minnesota Rep. Dean Phillips continues to consider one).

Meantime, a distinctive problem for Biden is that even as voters harbor concerns about his staying power for another four years, his running mate, Vice President Kamala Harris, has been singularly unsuccessful in constructing a solid image of competence. Her approval poll ratings are even lower than Biden's, as weak as any vice president's since such polling began. Her fatuous ramblings have become a comic internet staple.

One could make a decent argument that Biden's political prospects — and the good of the country — would be served by replacing Harris with a figure who inspires more confidence that the presidency would be in trustworthy hands should the office become vacant.

Jettisoning a running mate isn't easy (especially one who has broken a gender and a racial barrier). Denying renomination to a president is considerably harder. But both things have happened. Return with us now to another whirlwind tour of yesteryear, if only for another reminder that American politics has had disordered moments before.

No more years

Seven U.S. presidents desired but were denied second nominations by their parties, although they varied in how determinedly they sought an encore. It's striking that six of the seven had succeeded to the White House after the death of a president.

John Tyler: A gentlemanly but rigid Virginia plantation owner, he was a ticket-balancing vice presidential nominee for the Whig Party when it was well on its way to being torn apart by the slavery dispute. His single gridlocked term began when President William Henry Harrison got sick at his 1840 inauguration and died within weeks.

Millard Fillmore: Another compromise vice president, this New Yorker was more of a southern sympathizer than southerner and Mexican War hero President Zachary Taylor. Taylor's 1850 death allowed Fillmore to sign the much-despised Fugitive Slave Act.

Franklin Pierce: Plagued by alcoholism, family tragedy and inflexible "states' rights" ideology, the New Englander supported opening western territories to slavery, pushing the nation toward Civil War in the mid 1850s.

Andrew Johnson: An anti-secession Tennessean, he became Abraham Lincoln's second-term running mate in 1864. Lincoln's murder led to Johnson's strife-filled presidency, impeachment and acquittal.

Chester A. Arthur: A notorious New York spoilsman, nominated for vice president to placate political bosses in the golden age of machine politics, Arthur made powerful enemies championing Civil Service reform as president after the 1881 assassination of James Garfield.

Lyndon Johnson: The Texan became a powerful president in many ways after John Kennedy's assassination. But tormented by Vietnam War-era polarization and humiliated by a close early primary contest, Johnson shocked America by abandoning his bid for renomination in March 1968.

A seventh case was a little different: In 1912, former President Theodore Roosevelt, who had entered the White House after William McKinley's shooting and regretted a self-imposed term limit, challenged President William Howard Taft, his own former Secretary of War, for the GOP nomination. He failed and launched a formidable third-party bid, throwing the election to Democrat Woodrow Wilson.

But if even so potent a political force as Teddy Roosevelt could falter in a comeback attempt, one president did succeed in turning the tables the way Trump hopes to do. Grover Cleveland ousted Benjamin Harrison in 1892, having lost his first re-election bid to Harrison four years earlier.

A pattern is plain. Most chief executives dumped by their parties were jettisoned during America's most chaotically divisive eras — the Civil War and the 1960s. Time will tell whether today's political tempest has similar centrifugal energies.

Thanks for your service

Among vice presidents, Aaron Burr left a unique mark, if not a scar. His attempt to snatch the presidency away from Thomas Jefferson in 1800 after a tie vote in the Electoral College led to the creation of presidential tickets and the concept of "running mates" in the 12th Amendment to the U.S. Constitution. Burr wouldn't have been renominated in 1804 even if he hadn't killed Alexander Hamilton in a duel that year.

John C. Calhoun: America's two-party system was still evolving when the fierce advocate of slavery was elected vice president under both John Quincy Adams in 1824 and Andrew Jackson, who ousted Adams four years later. But Calhoun and Jackson clashed continually and the South Carolinian resigned in 1832.

Hannibal Hamlin: Lincoln's first vice president, displaced by unionist hero Andrew Johnson, Hamlin was the first of three well-forgotten late 19th century vice presidents dropped from tickets. The others were Schuyler Colfax, dumped by Ulysses Grant amid one of his administration's many scandals; and Levi Morton, dropped by President Benjamin Harrison in 1892.

John Nance Garner: One of America's most colorful vice presidents, "Cactus Jack" is less well remembered than is his verdict on the vice presidency as an office "not worth a bucket of warm spit." The conservative Texan was dropped after he challenged Franklin Roosevelt's bid for a third presidential nomination in 1940. Another substantial figure, New Deal Agriculture Secretary Henry Wallace, then became vice president, only to be discarded in 1944 as too liberal.

Nelson Rockefeller: The administration of President Richard Nixon and the Watergate scandal that forced his resignation brought unprecedented turmoil to the vice presidency. Combative Spiro T. Agnew resigned over scandals of his own in 1973 and mild-mannered Gerald Ford became vice president. When Nixon resigned the next year, liberal Republican Nelson Rockefeller became VP. But he was dropped in favor of more conservative Kansas Sen. Bob Dole when Ford unsuccessfully ran for re-election 1976.

Clearly, the need for a political repositioning is what's often forced vice presidents from tickets. Here too, today's conditions might fit the pattern.

D.J. Tice is at doug.tice@startribune.com.