This number suggests a MAJOR Democratic wave in 2018

(CNN)In the aftermath of Roy Moore's stunning Senate election loss in Alabama on Tuesday night, Republicans were quick to note that the circumstances in the state made drawing any conclusions impossible.

Moore, after all, was a hugely divisive figure even before a series of women came out over the past six weeks to allege that he had pursued relationships with them when they were teenagers and he was in his 30s. He was someone who had consistently underperformed compared to the average Republican candidate in past races. He ran an antiquated and tone-deaf campaign. And so on and so forth.
All true!
But, context!
    If the Moore loss to Doug Jones -- in a state that went for President Donald Trump by almost 28 points only 13 months ago -- was the only piece of evidence we had to analyze the current national environment, then it would be hasty to draw any sort of conclusion from it.
    Luckily for us, we have 538's Harry Enten! And, in particular, this great chart that Enten posted Wednesday on Twitter that shows how consistent the Alabama result is with other special elections so far in 2017:
    "Yes, AL-SEN is a bit of an outlier, but this table tells the story," tweeted Enten. "This a terrible national environment for the GOP."
    What the chart shows is that, time and time again over the past year, Democrats have drastically overperformed how the party's presidential nominee did in those same House districts and states. (The Partisan Voting Index is a way to compare every district in the country to every other district in the country based on presidential voting performance over the last two presidential elections. If interested, much more on PVI is here.)
    The average Democratic overperformance?16 points!
    If every Democrat running for House and Senate in 2018 outperformed by 16 points the average vote of Barack Obama in 2012 and Hillary Clinton in 2016 in their district or state, Democrats would have huge majorities in both chambers.
    That, of course, won't happen. But the Democratic overperformance documented by Enten suggests that the Democratic base is raring to go vote -- anytime and anywhere. And that the Republican base is, well, not.
    Combine that fact with the massive generic ballot lead -- as high as 15 points! -- that Democrats currently enjoy over Republicans, and you don't need a weatherman to know which way the wind blows. It's a gale force wind blasting Republicans in the face right about now.