Why did southern senators initially block the organization of the kansas and nebraska territories?
they thought the railroad that would be built there would only benefit the north.
they did not think the area’s american indians should be moved to oklahoma.
they worried that the area’s american indians would be relocated to the south.
they were afraid the admission of new free states would tip the balance.

The correct answer is they were afraid the admission of new free states would tip the balance.

Southern senators were concerned in terms of representation in Congress. In this case, Southern states did not want to add Kansas and Nebraska as states because the Missouri Compromise stated that these two territories would be free states if they entered the Union. This was bad for Southern senators, as it would mean more members of Congress who may be opposed to the idea of slavery and may try to get rid of it. This is what is meant by "tipping the balance." Southerners were worried that there would be more Congressmen against the institution of slavery, who could use their political power to get rid of the institution altogether.

theodore roosevelt 26th u.s. president : i admire his energy and passion. he was a fundamentally good man, brilliantly intelligent, possessed of extraordinary will and ability, supremely self-confident, bold, egalitarian, idealistic…. , lord, can we have him back?