[Ditter]

I have never heard the term “doughfaced Northerner” before but I would think it was rather like what the name “redneck” originally meant. A redneck means someone who works in the sun and doesn't tan very well and their neck (and face) turn red. Usually someone of Scot/Irish heritage. A “doughfaced northerner” could mean someone with a very pale complexion who works inside and doesn't get very tanned. .......... Or I am just a simple Texas girl who looks for the simple explanation.

[BroJoeK]

Ditter: "A “doughfaced northerner” could mean someone with a very pale complexion who works inside and doesn't get very tanned."

Here is the most complete explanation I've seen of the origins and meanings of the term "Doughface".

It was coined by Southerners as a term of disparagement to describe their Northern supporters, and may have originated as "Doe face", meaning a skittish, easily frightened female deer.
The word "Dough face" first appears around 1820.

But I like your suggestion of Northerners with pasty white, untanned faces being the opposite of Southern "rednecks"
The word "redneck" goes back even further:

"In Scotland in the 1640s, the Covenanters rejected rule by bishops, often signing manifestos using their own blood.
Some wore red cloth around their neck to signify their position, and were called rednecks by the Scottish ruling class to denote that they were the rebels in what came to be known as The Bishop's War that preceded the rise of Cromwell.[21][22]
Eventually, the term began to mean simply "Presbyterian", especially in communities along the Scottish border.
Because of the large number of Scottish immigrants in the pre-revolutionary American south, some historians have suggested that this may be the origin of the term in the United States.[23]

"Dictionaries document the earliest American citation of the term's use for Presbyterians in 1830, as 'a name bestowed upon the Presbyterians of Fayetteville [North Carolina]'. "

I like that too: "Redneck" means Presbyterian. Who knew?

;-)