After the smoke cleared, and people realized that Jeff Van Drew had changed his party status over to the Republicans....it required some survey of the 2nd District of New Jersey.
This is the district to the far south of New Jersey. It is 75-percent white and a working-class type district. Blacks make up only around 10-percent of the voters, and Latinos make up around the same number. Note: don't use Wiki for this Demographics business, because their numbers add up to around 110-percent.
While it's true that Obama won with 53-percent of the local vote in both 2008 and 2012.....Trump won with 50.6 percent (Hillary only carried 46 percent).
It's also true that if you use data from the 1940s to present....about every twenty years....the seat flips from the GOP to the Democrats, and then back.
The previous Representative? Frank LoBiondo. From 1995 on, Frank won with 60-plus percent of the vote. After he retired? Van Drew won with 53 percent of the vote (2018).
The odds of Van Drew winning in 2020, if he'd stayed a Democrat? I'd give it less than 30-percent odds. Part of this problem would have been Blacks flipping votes over to Trump, and the approaching Trump wave.