With the apparent win of Democrat Conor Lamb over Republican Rick Saccone in Pennsylvania's 18th district Tuesday, the Republican Party would do well to consider the gravity of their situation -- solidly conservative seats might not stand up to Democratic challenges this year.
A CNN analysis using the Cook Political Report's Partisan Voting Index, or PVI, shows that a full 119 districts stand on less solid ground than Pennsylvania's 18th in terms of how far right they leaned in the past two election cycles.
And Democrats need only flip 24 of those seats (23 if the vote count hands Lamb a victory) to realize a majority in the House.
The goal of the PVI is to compare every congressional district to every other congressional district based on how it has performed in each of the last two presidential elections.
So, in the case of PA-18, it has a PVI of R+11, meaning that in the last two presidential elections it has performed 11 points more Republican than the nation as a whole.
That PVI score makes Pennsylvania's 18th district the 124th-most Republican district in the country. (The most Republican district in the country is Texas Rep. Mac Thornberry's 13th, with a PVI rating of R+33.)
According to the most recent edition of the Cook PVI ratings, there are 119 districts currently held by Republicans that have a lower PVI rating than Pennsylvania's 18th.
That's exactly half of the 238 seats Republicans currently hold -- HALF. It's far beyond the 23 seats that Hillary Clinton won in 2016 that are currently represented by a Republican. It's roughly five times as many seats as Democrats would need to pick up -- 23 assuming Lamb wins -- to retake the House majority come November. And it's well more than the 74 seats that the Cook Report ranks as marginally competitive as of today.
Does this mean Democrats will have an easy time flipping those seats? Not necessarily -- but it does mean that Republicans would do well to heed what appears to be a blue wave preparing to wash across the country.