UPDATE: FiveThirtyEight's Harry Enten ("5 Takeaways From The Georgia 6 Special Election") is pretty much in line with what I think Ossoff's showing augurs for Democrats nationwide -- good but no realignment:
The result is consistent with a pro-Democratic national environment
There’s some chatter out there that Ossoff’s showing is a bad sign for Democrats. He didn’t clear 50 percent, they say, and he barely improved on Clinton’s performance in Georgia 6.
I think that’s a flawed argument.
For one, Clinton had already greatly improved on previous Democrats’ performance in Georgia 6. She lost to Trump there by only 1.5 percentage points. Former President Barack Obama lost the district by 23 points in 2012, as did Democratic congressional candidate Rodney Stooksbury in 2016.
So if you’re just looking at the 2016 presidential result as your benchmark you’re probably missing something. Instead, our best estimate of the partisan lean of a district is to take a weighted average 2 of its past two presidential election results. By that measure, a Democrat would be expected to lose Georgia 6 by 9.5 percentage points in a neutral national environment (one in which the two parties fought to a tie nationally). Democrats did far better than that on Tuesday, losing by 2 points. The Democratic candidates combined took 49 percent to the Republicans’ 51 percent.
What this means for the 2018 midterm is less clear
The Republican +2 aggregate margin in Georgia 6 implies a national environment in which Democrats are competitive in a bunch of GOP-held House seats in 2018. According to the weighted average of the past two presidential elections, there are 48 House districts that were won by GOP candidates in 2016 that are bluer than Georgia 6. The district’s Round 1 results suggest Republicans could lose a good portion of those 48 seats. And Democrats need to win just 24 Republican-held seats for control of the House.
That’s clearly a good sign for Democrats.
Of course, the national political environment could change between now and November 2018. Moreover, the Georgia 6 result isn’t anywhere near as strong for Democrats as last week’s result in the special election in Kansas’s 4th Congressional District. The Georgia 6 Democrats outperformed the weighted average by 7.5 percentage points. In Kansas 4, Democrat James Thompson beat it by 22 points.
Still, that’s the difference between a good Democratic year in 2018, with the House in play, and a crazily, ridiculously good Democratic year, with the House a foregone conclusion to flip to Democratic control. (Again, that’s if the national political winds don’t shift between now and then — an unlikely proposition.)
The truth is we need a larger sample size of special election results before understanding what Kansas 4 and Georgia 6 tell us about the midterms.
A couple points shy of avoiding a runoff in Georgia's 6th CD, Democratic Great White Hope Jon Ossoff will now face Republican Karen Handel in a June second round.
At 48.1%, Ossoff probably hit the upper end of his support in the district. It is going to be hard for him to keep his professional staff and volunteers together over a two-month spring stretch.
The race was noteworthy in the final days for Trump inserting himself directly. As Jonathan Martin and Richard Fausset point out in "Jon Ossoff, a Democrat, Narrowly Misses Outright Win in Georgia House Race":
In an illustration of how nationalized the race became, 95 percent of Mr. Ossoff’s fund-raising haul was from out of state, and even more was from outside the district, where the candidate himself does not reside (though he grew up there).
Republicans blistered him on this score and much else, a kitchen-sink campaign that totaled $5 million yet also stirred muttering within the party about why there had not been a more coherent approach to a district they knew would be competitive, given Mr. Trump’s weakness here. But the unrelenting Republican assault eventually paid off, raising Mr. Ossoff’s negative ratings and nudging conservative voters to show up for an unusual spring election.A combination of non-stop attack ads and the difficulty of keeping people motivated month after month means that Ossoff likely loses in June. Not the singular realigning election moment that the Democratic Party was seeking.