Court cases related to the 12th Amendment of the U.S. Constitution focus on contested presidential elections. One of the more famous 12th Amendment court cases occurred following the 2000 election between Al Gore and George W. Bush, when Gore challenged the validity of certain electoral college votes.
The 12th Amendment was added to the Constitution following the Presidential election of 1800 and changed the way that the U.S. President and Vice-President are elected. This amendment required all members of the electoral college to place one vote for the president and one for the vice-president. In the event that no candidate had a majority of votes, the House of Representatives would then select the president from the top three candidates.
Prior to this, each elector had two votes but there was no distinction between voting for the president and vice-president. Similarly, the House originally had to select the president from the top five candidates, which led to a catastrophe in 1800, when the House had to have 36 rounds of voting before finally deciding to elect Thomas Jefferson.
One of the provisions in the 12th Amendment, known as the Habitation Clause, states that at least one of the elector's votes must be for a candidate who is from outside his state. This is the clause that was used following the 2000 election, when it was argued that Dick Cheney was a resident of Texas despite claiming to live in Wyoming. The court eventually ruled in favor of Bush and Cheney, but if it had not, then the Texas electors' votes would have been invalid and Gore would have become president.