Without the use of machinery many Americans will be employed to do various jobs. Their unemployment rate during that time will decrease. Another consideration is that there is a need for expertise in handling heavy machinery. One must be learned enough not only to drive heavy machinery but also to operate it and maintain its good condition.
Southern Democrats is the correct answer.
It was the issue of slavery which mainly divided US into northern and southern states and further Democratic party into southern Democrats and Northern Democrats. The Southern Democrats were pro-slavery and thus challenged the Northwest Ordinance's prohibition of slavery by the late 1850s.