Final answer:
The Northeastern Federalists discussed the possibility of secession from the Union if the War of 1812 did not end at the Hartford Convention, which ultimately damaged their reputation and led to their political decline.
Step-by-step explanation:
Northeastern Federalists threatened to secede from the Union during the War of 1812 if the war did not end. The event where these discussions took place was the Hartford Convention. Delegates from Connecticut, Massachusetts, Rhode Island, New Hampshire, and Vermont met in Hartford, Connecticut, to consider the possibility of secession because of their dissatisfaction with the war's progress and its economic impact on the New England region.
However, their considerations were ultimately overshadowed by news of Andrew Jackson’s victory at the Battle of New Orleans and the signing of the Treaty of Ghent, which officially ended the war. These events, particularly the Hartford Convention, severely damaged the Federalist Party's reputation and led to its ultimate demise in American politics.