Marc Egnal's new book Clash of Extremes: The Economic Origins of the Civil War contains a detailed review of the statistical evidence showing that Whigs tended to be wealthier than Democrats, in both the North and South. But I really got a laugh out this little piece of anecdotal evidence (emphasis added):
Seventeen-year-old Varina Howell was struck by the tall, slender, intense planter she had just met. "I do not know whether this Mr. Jefferson Davis is young or old," she wrote her mother in December 1843. "He looks both at times. . . . He impresses me as a remarkable kind of man, but of uncertain temper, and has a way of taking for granted that everybody agrees with him when he expresses an opinion, which offends me; yet is most agreeable and has a peculiarly sweet voice and a winning manner of asserting himself." But Howell was puzzled by Davis's politics. She told her mother: "Would you believe it, he is refined and cultivated, and yet he is a Democrat!" Her parents and (as she later recollected) "most of the gentlefolk of Natchez," where she was raised, were Whigs.