Why did some northerners object to dividing the Nebraska Territory in two Douglas had already proposed the idea of allowing popular sovereignty in the?

Some Northerners objected to dividing the Nebraska Territory because they feared it would expand slavery into areas where it had been previously restricted. By allowing popular sovereignty, the decision of whether to allow slavery would be left to the settlers, which many Northerners believed undermined the Missouri Compromise and could lead to the spread of slavery into free territories. Additionally, they viewed the division as a political maneuver to benefit slaveholding interests at the expense of free labor and values.