What was a fear of Southern senators if there were more free states than slave states?
The Southern Sentors feared that the free states would use their legislative power to hurt and cripple the south.
The fear that the free states would use their legislative power to hurt and cripple the south was not illogical. The tariff of abominations of 1828 was extremely unfair to the south. Taxes on imports that the south depended on were raised as much as 40%.
The tariffs were designed to promote industries in the north as the expense of the south. The south was being forced to sell their cotton to factories in the north for less money that the south could get from selling their cotton to England and France. The south feared that if the free states controlled both the House of representatives and the Senate the south would be taken advantage of.
The south also feared new laws against slavery. Already laws had been passed outlawing the importation of new slaves from outside the United States. Slave auctions in Washington DC had been outlawed. If the north has a majority in both the House and Senate slavery could be totally outlawed.