Why did the traditional two party system fail in the 1850's what role did third party movements play in heightening sectional tensions during this period?

It was because of the slavery that the traditional two party system fail in 1850's. Democrats were broken and in half over slavery and divided into North and South parties. Similar thing happened to the Wigs as many of their members went for the third party movements. One these movements would become the Republican party.

The traditional two-party system fails in the 1850s due to the Slavery tore apart America's political parties during the 1850s.

Explanation:

Role of Third parties played during this period are:

Third parties are usually formed around social activists and causes. If the Third party is Neglected or their views are neglected by the two main parties then they might affect the Election result by taking away the votes or splitting the votes. Third Parties affect the Elections by bringing light on those issues which are neglected by the two mainstream parties.