Our project to calculate the 2020 presidential results for all 435 House seats nationwide heads down to Alabama, which is home to the Trumpiest congressional district in America. You can find our detailed calculations here, a large-size map of the results here, and our permanent, bookmarkable link for all 435 districts here.
The constituency that gave Donald Trump both his highest percentage of the vote and widest margin of victory in the nation is Alabama’s 4th Congressional District, which has been represented by Republican Rep. Robert Aderholt since 1997. Trump defeated Joe Biden in this seat, which is located in the north-central part of the state, 81-18, which was almost identical to his 80-17 performance against Hillary Clinton four years before.
The 4th gave Trump his best showing in any of the 411 congressional districts we’ve released 2020 data for so far, and we're confident there's no chance that it'll get displaced when we finish calculating results for our two remaining states, Louisiana and Pennsylvania. And the result is no surprise: In 2016, Trump also earned his biggest share of the vote nationwide in the 4th, though his net margin was just a touch higher in Texas' 13th.
There are a few reasons why Alabama’s 4th is so deeply conservative. The district is both extremely rural and heavily white, but what makes it singular is that it has the highest percentage of evangelical residents in America, with approximately 54% of residents identifying as such. It's also in the bottom quintile in the nation both in terms of diversity and its level of educational attainment, a category exclusively occupied by deeply Republican districts.
However, while it’s now impossible to imagine Aderholt being threatened by a Democrat, he only barely won his first election for a previous version of the 4th nearly a quarter century ago. In 1996, Aderholt ran to succeed retiring Rep. Tom Bevill, who was a prominent member of a powerful bloc of conservative Democrats nicknamed the “boll weevils.” Bevill himself had won his final term two years before without any opposition even as Republicans were flipping numerous Southern districts en route to taking their first House majority in 40 years, and local Democrats still demonstrated strength further down the ballot.
The Democrats nominated former state Sen. Bob Wilson, who had narrowly lost reelection in 1994 but was still capable of putting up a strong fight. Wilson argued he’d secure needed appropriations for his seat “in the Tom Bevill tradition,” but he also focused on his opposition to abortion and his membership in the NRA.
Aderholt, who was a local judge at the time, tied Wilson to the national Democratic leadership and argued that he'd be no substitute for Bevill. Both parties saw the race as a priority, and Speaker Newt Gingrich stumped for Aderholt in a cycle where his newly minted majority seemed to be on the line. Ultimately, Aderholt pulled off a 50-48 victory as Bob Dole was defeating Bill Clinton 48-43 in the district.
Wilson sought a rematch in 1998 but lost his primary to Donald Bevill, the son of the former congressman. The general election wasn’t so competitive this time, though, as Aderholt won 56-44. That didn't quite bring an end to Democratic attempts to win back their old turf, but the next cycle did: Former Alabama First Lady Marsha Folsom lost the 2000 election to Aderholt by a punishing 61-37 spread as George W. Bush was pulling off a 59-39 victory. Team Blue didn’t field a challenger two years later, and Aderholt has been completely safe ever since.
Trump didn’t come close to matching his high-water mark elsewhere in Alabama, but he still won at least 63% of the vote in the state’s five remaining GOP-held districts. Biden, meanwhile, scored a 71-28 victory in Democratic Rep. Terri Sewell’s 7th District, a constituency that Republican mapmakers drew to take in as many African American voters as possible.
Finally, there’s one methodological issue we want to address in Alabama, which, like many other states, does not assign every vote to a precinct. This is not a new issue, and we have techniques that estimate how to divvy up unassigned votes like these between districts.
However, the coronavirus pandemic led to a major expansion in the number of votes cast before Election Day, and in Alabama, that meant a much larger than usual proportion were not assigned to a congressional district: In 2016, these unassigned votes only made up 4% of the total vote in the seven counties that are split between multiple districts, but that figure swelled to 14% in 2020.
Even with this issue, there's no question which presidential candidate won each of the state’s House seats; still, we strive to make our estimates as precise as possible. Luckily, Alabama does include the total number of unassigned votes cast in each district in each county (though not their breakdowns by candidate), which is important information that is rarely available.
For example, in Jefferson County, which is the largest in the state, approximately 327,000 ballots were cast, with about 50,000 not assigned to any precinct. However, thanks to the state's data, we do know that 26,000 of these unassigned ballots were cast in the 6th Congressional District and the balance cast in the 7th.
We use this information to more accurately assign these votes by congressional district. We start by assuming that how a candidate’s supporters choose to cast their ballots is similar no matter where they live. For example, if 30% of Biden voters choose to vote absentee in District A, we assume somewhere around 30% of Biden voters will also choose to vote absentee in District B. (We've validated this assumption by testing it in other states that make more detailed vote breakdowns available.) This assumption is then used to calculate an initial estimate of votes for each candidate in each district in a county.
We then use the total number of unassigned votes cast in each district in each county to adjust our initial estimates so the totals match. Finally, we adjust the number of votes again so the number of unassigned votes for each candidate in the whole county matches the official results.
These estimates are not perfect, and they do introduce some error into our final numbers; we suspect the error for Alabama districts is about one percentage point or less for a candidate’s vote share districtwide, based on calculations in other states where vote count by type of ballot is known. However, we believe this method allows us to assign these previously unassigned votes as precisely as possible to their proper congressional district.