Why do third parties usually not last very long in the american two party system

For the very reason that us as Americans have been in this two-party system for so long that we would want to keep this tradition rather than to add another party, and oppose eachother even more. Also, voters feel that having a third party vote is irrelevant because it is less likely to be voted for and won over.

in february 1787, congress decided that a convention should be convened to revise the articles of confederation, the nation’s first constitution. in may, 55 delegates came to philadelphia, and the constitutional convention began. debates erupted over representation in congress, over slavery, and over the new executive branch. the debates continued through four hot and muggy months. but eventually the delegates reached compromises, and on september 17, they produced the u.s. constitution, replacing the articles with the governing document that has functioned effectively for more than 200 years.