Let’s take two fairly obvious data-driven conclusions from the 2016 election and see if there’s any link between them.
The first conclusion: Education was almost everything in explaining the results of the race. Donald Trump substantially improved on Mitt Romney’s performance among voters without college degrees — especially white voters without college degrees. Hillary Clinton somewhat improved on President Obama’s performance with college-educated voters. The link between education levels and the shift in the vote is robust, even when controlling for other factors, such as income levels.
The second conclusion: The polling was bad. Actually, let me amend that: The polling wasn’t that bad. (Reporters and analysts should have been more prepared for the possibility that Trump might win. We’re going to keep being really annoying about this.)
With Clinton’s lead in the popular vote still expanding, the national polls are going to wind up having been pretty good (they showed her winning by 3 to 4 percentage points, and she’ll eventually win by about 2 points). The state polls? Not so hot. What matters, though, is not only the magnitude of the error in the state polls but the direction of it. The errors were correlated from state to state, and Clinton underperformed in a trio of states in the Rust Belt — Michigan, Wisconsin and Pennsylvania — that were supposed to have been part of her firewall; that underperformance cost her the Electoral College.
So, are these two things connected? Did Trump beat his polls in states with large numbers of white voters without college degrees?
The short answer is “yes.”
And the data is pretty convincing: there are 19 states that have a majority of white voters without college degrees. Donald Trump beat the averages of state polls in 18 of those 19 states (all but Oregon) and he beat them by an average of 7.6 points. He beat Ohio's and Wisconsin's state polls by 6 points,, Michigan's by 4, Pennsylvania's by 5, NC's by 4, and Florida's by 2. He won all of those states.
In blood red states like Kentucky, he beat his state polling average by 11 points and by 14 in WV..
In other words, where national polling was correct (Clinton will end up winning the national popular vote by 2.5%-3% or so, where the polls had her) state polling in 2016 was 100% useless.
The same thing that happened in Kentucky in 2015 with Matt Bevin versus Jack Conway, the poll that was off by 13 points? In 2016 it was national, and every single polling outfit messed up at the state level.
It's worth thinking about. The reality however?
So Clinton lost Michigan by ~0.2%, Wisconsin by ~0.7%, Pennsylvania by ~0.8%. https://t.co/wbnGFEmcen— Nate Silver (@NateSilver538) December 1, 2016
With this update:— Charles Gaba (@charles_gaba) December 1, 2016
WI: Hillary down 22,177
MI: Hillary down 10,704
PA: Hillary down 46,435
Total: 79,316 https://t.co/pcOqvSQlNz
All less than Jill Stein's total in each state.
This is why Trump will be President in January.