Former Vice President Mike Pence filed paperwork to declare his candidacy for president on June 5, 2023 – placing him in unusual ranks.

While 18 of the 49 former vice presidents have gone on to run for president, it’s rare for vice presidents to run against their former bosses. Six of these former vice presidents, including President Joe Biden, were ultimately elected president.

Pence, alongside other candidates, is expected to officially announce his bid on June 7.

Pence and former President Donald Trump have had a complicated relationship. Pence’s devout conservative evangelical Christianity was a crucial ingredient in helping carry Trump to victory in 2016.

But Trump blames Pence for the Jan. 6, 2021, Capitol riots and has said he is angry with him for certifying the 2020 election results. Pence remained trapped at the Capitol during the attack, which Trump did nothing to try to end.

There are only a few other times in American history that are vaguely similar to the unfolding battle over who will become the Republican presidential nominee. Both were extraordinarily bitter, and centuries later, their strife still makes historians and experts on the presidency – including myself – raise eyebrows.

There is one other time in history when a vice president ran against the president he served with in office.

In the election of 1800, Vice President Thomas Jefferson challenged incumbent President John Adams. Adams had won the presidency in 1796, and Jefferson was runner-up, making him vice president. Until 1804, the person who came in first in a presidential election became commander in chief, while the person who brought in the second-most votes became vice president.

Jefferson, though, wanted the top job.

And so when Adams ran for reelection, Jefferson ran against him in one of the most notorious races in American history.

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