Why did white southerners remain committed to the institution of slavery and its expansion in 1860?

The white Southerners remain in favour of slavery because slaves made the South prosper and wealthy (Cotton King).

Explanation:

The southerners remain committed to the institution of slavery because it was the backbone of their economy. The Southern states were the growers of the cash crops since its colonial period because of its geographical condition and climate which provide a hot with mild winters.The Southern states depended on the slavery system in socially and economically because they generated wealth for the white Southerns by forcing them to work in the cotton plantations.      

answer; (a) he was a u.s senator for 38 years;

the answer is the government.