2012 was the "10 Commandments" referendum election that was to *re-elect* Moore as chief justice in Alabama after the black robed tyrants threw him out. It was a single issue election, highly polarized. It offers an *extreme* example ... just like the Moore / Jones election today. I would expect similar performance. I'm glad you pointed it out. Let's compare :
2012 Moore / Vance : 110,815 + 188,916 = 299,731
2017 Moore / Jones : 66,309 + 149,522 = 215,831
Given the similarity in polarization between these elections, With voter turnout down 83,900 votes, I still would expect Moore to have received about 87,707 votes in Jefferson County (110,815 x 149,522 / 188,916). But only 66,309 votes were counted for Moore. There are 21,398 votes for Moore that I would have expected in a highly polarized election like this one that did not materialize.
In 2012, Repiblicans had other positions to vote for that drew them to the polls. He may have also benefited from Straight Ticket voters. This time when it was just Roy on the ticket, folks either stayed home or crossed over.