The results of Tuesday's Pennsylvania special election should be an unbearably loud fire alarm for national Republicans about the state of public dissatisfaction with their party. If they aren't covering their ears and sprinting for the exits, they are making a fatal error.

In a special election to fill the seat of disgraced GOP Rep. Tim Murphy, the results were too close to call early Wednesday morning. But with 100 percent of precincts reporting, Democrat Conor Lamb appeared to have narrowly defeated the hand-picked candidate of the Pennsylvania Republican Party, a dull state legislator and proud Trumper called Rick Saccone. Around 1 a.m., Lamb declared victory, though Saccone insisted "it's not over yet." A recount remained possible, but that one would even be needed in such a deep-red district was a warning sign for Republicans.

While special elections are silly and wasteful, Tuesday's election was still huge for the Democrats and their chances of regaining power this November. Repeat this simple mantra, my little donkeys: President Trump is not magic. His incompetence is killing the GOP. His partisans are deserting him even in his strongholds and his party is now set for a historic drubbing that might eclipse even the "shellacking" delivered to former President Obama's Democrats in 2010. Republican legislators on the fence about retiring will have their answer: Golfing in Florida beats this kind of humiliation.

Democrats should be elated. If Republicans aren't safe in PA-18, they aren't safe anywhere. Trump carried Pennsylvania's 18th district by 19.6 points, and last night's showing was a shocking 20-point swing away from the 2016 results. Republican turnout collapsed. If you take last night's results literally and seriously, they could put more than 120 Republican seats in play in November. While many of those districts will have strong, popular incumbents and other factors that will make them far out of reach for Democrats, Lamb's strong showing must be terrifying for Republican strategists. Even 10 or 20 additional winnable districts for the Democrats could have a transformative effect on their chances of taking over the House.

PA-18 isn't some strange Obama-Trump situation either, where a formerly competitive district is reverting to a pre-2016 status quo. Pennsylvania's 18th went deep red during the Bush administration and has been a layup for the national party ever since. While he wasn't a great candidate, Saccone was scandal-free, had aligned himself closely with the Trump administration's positions, boasted the full (if panicked) support of the national party, and was rewarded with his own personal rally headlined by the president himself over the weekend. If that's not enough to put an overwhelmingly red district away for the GOP, there is really no salvaging Paul Ryan's sordid majority. Sure, Saccone's fundraising was mediocre, but it might be time for the national GOP to wonder whether that was the candidate's fault or Trump's.

Does Tuesday's election mean Democrats will definitely coast to victory this fall? It's best to look at a rolling average of special election results to get a sense of how things stand for the midterms. In the last six cycles, special election results have been broadly predictive of who will triumph in the all-important midterms. And these elections results tell a story of the president's most crucial supporters not caring enough to turn out, and being overwhelmed by energized progressives.

Are Democrats going to do 20 points better in the midterms than they did in 2016? A few days ago I would have said "almost certainly not" — those are veto-proof majority numbers that would make Nancy Pelosi the de facto president, and even if Republican turnout is depressed in November, it will definitely be substantially higher than it was last night in Pennsylvania. The overall partisan lean of Pennsylvania's 18th is about +11 for the Republicans, a much more realistic number to expect than 20. Still, with the midterms creeping closer by the day, Republicans are running out of time to save their majority.

A bigger, deeper question is this: Is Trump's support collapsing even in his strongest areas? One detail that really should worry the president's re-election team is that some of the largest swings toward Team Blue seem to be happening in Trump landslide districts like PA-18. For instance, Democrats picked up just 4 points against the overall 9-point Republican lean in Georgia's 6th district in a June 2017 special election. But particularly in state elections like Missouri's 97th House district, Democrats are winning seats or making serious inroads in places that Trump carried by 25 points or more. If the president's support continues to collapse in deep red districts around the country at even a fraction of the rate it did in Pennsylvania last night, Trump will have a very difficult time being competitive in 2020.

On the one hand, these numbers might cheer GOP strategists who are feeling glum this morning. After all, if the swing against the party is somewhat less significant (if still serious) in competitive districts, it's possible that a modest recovery in Republican numbers on the generic ballot might allow them to hold some critical seats in close races around the country and perhaps their majority. But the president, who already lost the popular vote to the unloved Democratic nominee Hillary Clinton in 2016, can ill afford to bleed out double-digit support in strongholds like Pennsylvania's 18th. If anything, given the ongoing demographic transformation of the United States, the slow dying off of the Republicans' most loyal elderly voters, and the enormous advantage Democrats enjoy among millennial voters, Republicans need to increase their support in areas like this to have any chance of holding onto the presidency beyond 2020.

The only thing Republicans increased Tuesday night was their anxiety levels.