Only three Vice Presidents faced this situation before the Twelfth Amendment was ratified shortly before the presidential election of 1804.

John Adams was the first Vice President during Washington's administration. There wasn't much partisan tension early on. Both were Federalists and Washington faced almost no partisan criticism during his first term.

Adams correctly interpreted the new Constitution's explanation of the Vice President's main duties: serving as President of the Senate. But his assumption that he would be a kind of sagely parliamentarian who would guide senators through their debates on bills was rejected by the senators themselves. He was disappointed to find that the job mostly consisted of banging a gavel and formally calling on senators who wanted to address the chamber instead. In fairness to Adams, no one had ever held the office before, so it's not like anyone could be completely sure what the Vice President was supposed to, you know, do. The tension between Adams and the senators was of a personal nature, not a partisan dispute.

After Washington opted to retire, Adams was elected president in 1796 and Thomas Jefferson - having received the second-most electoral votes - became Vice President. This quickly became problematic. By this time the two early political parties (Federalists and Democratic-Republicans) were becoming more organized and adversarial. Jefferson became the de facto Democratic-Republican leader and began surreptitiously coordinating party activities against Adams and the Federalists. This solidified a rift between Adams and Jefferson that would continue until 1812, after both had retired from politics. Their feud was especially painful because they had previously been close friends since the 1770s. Vice President Jefferson became President Adams' top political enemy. He used surrogates to criticize Adams in the harshest of terms and worked to undermine him in just about every way possible.

Jefferson opposed Adams in the presidential election of 1800. This was the only time that a sitting Vice President has ever run against a sitting president. The Democratic-Republicans intended Aaron Burr as their vice presidential "nominee" and instructed their electors to vote for Jefferson and Burr. (At the time, each elector could vote for two candidates.) The plan was to stack the top two electoral vote getters to both be Democratic-Republicans so that no Federalist could be elected President or Vice President. This was the first two-person presidential party ticket.

Unfortunately, the result wasn't what the Democratic-Republicans planned. Although Jefferson and Burr did finish in the top two, they were tied with the same number of electoral votes for president because the Constitution didn't provide for a way to cast a separate vote for Vice President. The House of Representatives had to break the presidential election stalemate. Jefferson expected Burr to step aside so that the Democratic-Republican congressmen who now controlled a House majority could make Jefferson president and Burr the new VP. That was the plan, right?

Burr, being the brilliant and devious politician that he was, saw an opportunity to become president with the help of Federalist votes. He knew that the Federalists couldn't stand Jefferson, so he offered himself as an alternative. This might have worked if Federalist leader Alexander Hamilton hadn't despised Burr even more than he hated Jefferson. Hamilton made sure Burr had to settle for VP instead.

Jefferson was incensed that Burr had jeopardized his election and turned Burr into a pariah within the party. He quietly presided over the Senate and became a marginal player in national politics. The Democratic-Republicans mobilized an effort to pass a constitutional amendment to make the President and Vice President into offices that were elected separately to prevent the kind of scheme that Burr attempted from ever happening again. Burr could see that he would not be a candidate for VP again.

He unsuccessfully ran for governor in New York. During that campaign, his war of words with Hamilton intensified, culminating in the famous duel in which Burr - while Vice President of the United States! - killed Hamilton. After leaving office, Burr was implicated in an effort to lead a secession movement in the western territories and spent a number of years in quasi-exile in England.

The original method of electing Vice Presidents proved to be the most problematic structural flaw in the Constitution during the early years of the Republic. Although Adams' early years as Vice President were pretty calm, the partisan backbiting became so acute that the Twelfth Amendment had to be ratified to prevent a future constitutional crisis. In hindsight it seems obvious that making a Vice President out of a new President's top election rival was a bad idea, but it didn't seem so dangerous before the rise of political parties.

Only three Vice Presidents faced this situation before the Twelfth Amendment was ratified shortly before the presidential election of 1804.

John Adams was the first Vice President during Washington's administration. There wasn't much partisan tension early on. Both were Federalists and Washington faced almost no partisan criticism during his first term.

Adams correctly interpreted the new Constitution's explanation of the Vice President's main duties: serving as President of the Senate. But his assumption that he would be a kind of sagely parliamentarian who would guide senators through their debates on bills was rejected by the senators themselves. He was disappointed to find that the job mostly consisted of banging a gavel and formally calling on senators who wanted to address the chamber instead. In fairness to Adams, no one had ever held the office before, so it's not like anyone could be completely sure what the Vice President was supposed to, you know, do. The tension between Adams and the senators was of a personal nature, not a partisan dispute.

After Washington opted to retire, Adams was elected president in 1796 and Thomas Jefferson - having received the second-most electoral votes - became Vice President. This quickly became problematic. By this time the two early political parties (Federalists and Democratic-Republicans) were becoming more organized and adversarial. Jefferson became the de facto Democratic-Republican leader and began surreptitiously coordinating party activities against Adams and the Federalists. This solidified a rift between Adams and Jefferson that would continue until 1812, after both had retired from politics. Their feud was especially painful because they had previously been close friends since the 1770s. Vice President Jefferson became President Adams' top political enemy. He used surrogates to criticize Adams in the harshest of terms and worked to undermine him in just about every way possible.

Jefferson opposed Adams in the presidential election of 1800. This was the only time that a sitting Vice President has ever run against a sitting president. The Democratic-Republicans intended Aaron Burr as their vice presidential "nominee" and instructed their electors to vote for Jefferson and Burr. (At the time, each elector could vote for two candidates.) The plan was to stack the top two electoral vote getters to both be Democratic-Republicans so that no Federalist could be elected President or Vice President. This was the first two-person presidential party ticket.

Unfortunately, the result wasn't what the Democratic-Republicans planned. Although Jefferson and Burr did finish in the top two, they were tied with the same number of electoral votes for president because the Constitution didn't provide for a way to cast a separate vote for Vice President. The House of Representatives had to break the presidential election stalemate. Jefferson expected Burr to step aside so that the Democratic-Republican congressmen who now controlled a House majority could make Jefferson president and Burr the new VP. That was the plan, right?

Burr, being the brilliant and devious politician that he was, saw an opportunity to become president with the help of Federalist votes. He knew that the Federalists couldn't stand Jefferson, so he offered himself as an alternative. This might have worked if Federalist leader Alexander Hamilton hadn't despised Burr even more than he hated Jefferson. Hamilton made sure Burr had to settle for VP instead.

Jefferson was incensed that Burr had jeopardized his election and turned Burr into a pariah within the party. He quietly presided over the Senate and became a marginal player in national politics. The Democratic-Republicans mobilized an effort to pass a constitutional amendment to make the President and Vice President into offices that were elected separately to prevent the kind of scheme that Burr attempted from ever happening again. Burr could see that he would not be a candidate for VP again.

He unsuccessfully ran for governor in New York. During that campaign, his war of words with Hamilton intensified, culminating in the famous duel in which Burr - while Vice President of the United States! - killed Hamilton. After leaving office, Burr was implicated in an effort to lead a secession movement in the western territories and spent a number of years in quasi-exile in England.

The original method of electing Vice Presidents proved to be the most problematic structural flaw in the Constitution during the early years of the Republic. Although Adams' early years as Vice President were pretty calm, the partisan backbiting became so acute that the Twelfth Amendment had to be ratified to prevent a future constitutional crisis. In hindsight it seems obvious that making a Vice President out of a new President's top election rival was a bad idea, but it didn't seem so dangerous before the rise of political parties.