Economics as in protecting the source of their wealth and power, i.e. slavery.
Slavery was part of the economics issue, but economics was the parent issue and slavery was the child issue. Yes, many politicians (who are not economists) made all sorts of stupid speeches.
If a person is going to quote a politician as if that person was brilliant, I don't want to see any further criticism of Trump from that person. After all, getting elected means you are now brilliant. By the way, Lincoln did promise to not interfere with slavery and even supported a constitutional amendment to protect it. Then war broke out.
Economics is too subtle for most people, and politicians aren't even less subtle.
What economic factor other than slavery made the difference? That's easy. Most Southerners didn't own slaves. Even then the South was more agrarian and the North more industrial. The industrial states and the agrarian states had different interests. The reason why the Democratic Party had an easier time dealing with these differences than the Whig Party has a lot to do with the platforms of each, and the economic implications of those platforms.
The North was industrial, and the South agrarian. Therefore if the South wanted manufactured goods, they either had to buy them from the North or buy them from England. If the South wanted to sell raw materials, they either had to sell them to the North or to England. It was in their own best interest to see where they could get the best prices.
The North and England were in competition for Southern business. There was one difference between the two of them, and that was that only one of them could use politics to distort economics - protective tariffs. When such tariffs pass, it means the agrarian South pays and the industrial North benefits. Inter-regional economic conflict. Then to make the situation worse, the Whig Party (and the Republican Party) wanted to use those funds raised to pay for all the roads, railroads, canals, and bridges that benefit only the North.
This conflict was compounded, but not caused, by slavery. Slavery makes it harder for a pre-industrial society to modernize, thereby holding back the South. Idiot politicians may have talked about defending slavery, but they were politicians and so even less aware of economic forces than the average unaware person.