Helms was an outright, unapologetic racist who didn't bother to hide it with dogwhistles. This would make him much harder for most of the North to swallow than Reagan, who was much more charismatic and better at selling conservatism to a wider audience. Some people who voted for Reagan in our timeline, repulsed by Helms, stick with Carter. And more go with Anderson than in our timeline as well. Carter hangs on as a result, despite the hostage crisis and the rest of the "malaise" in his presidency. People forget Carter was actually still the favorite until fairly close to the election, even against Reagan.
I'm guessing the map looks something like this, give or take a few states:
Carter: 408
Helms: 130
Popular vote something like:
Carter: 47%
Helms: 39%
Anderson: 11%
Ironically, some of the states that were closest in our timeline (namely, southern states) would likely be some of Helms's best, given who he is and where he's from. Though I do think Carter would keep it competitive in most of those states. And I think he would comfortably hold on to his home state of Georgia and the upper South aside from North Carolina. And he makes up for NC by narrowly gaining Virginia. I also think he might just barely hold on to Texas, and do better than before in the North and West due to Anderson splitting votes and Helms's lack of appeal to many voters in these areas.
