The part of the Constitution found in the executive branch would be “Article 2, section 1”. it states “The executive Power shall be vested in a President of the United States of America.”
Northerners had many politicians that didn't essentially care about reconstruction or African-Americans. They just went south to get into positions of power because the political area was open for newcomers since the old politicians in the South were the racists who led to the war. As they weren't that interested, the ideas of democracy soon ended and the policy of separate but equal was established which still enabled racism and segregation only in a legal manner.
The territorial expansion of the US and the question of whether or not slavery would be allowed in the new territories was perhaps the single greatest factor leading up to the war, since before expansion, slavery was mostly confined to the South.
