2018 is totally possible and given how pretty much every midterm in the past 40 years besides 1998, 2002, and 1982 is even probable.
You can say "muh ugly looking map", but trump's likely lack of popularity will make up for that, same way Johnson, Tumor, Ayotte, and Kirk got elected despite Obama's relative popularity in those states. 2016 and 2010 were favorable maps for Democrats to defend/take-back...the former failed, the latter barely held on.
All it takes is Heller, Flake, and one state to do it. And if Schumer and Co. stop with the high ground and do as McConnell once did, and Ellison can even match Kaine...even Nebraska could go into play.
And as for 2020, Tillis, Gardner, Perdue, and Sullivan are good spots if that fails.
The only hole in this is the rather uncanny ability to nab defeat from victory's wide maw.
Heitkamp is going to be in the cabinet in all likelihood, so you guys need two beyond Heller and Flake. And that's if you somehow keep all of McCaskill, Manchin, Tester, and Donnelly.
The Senate is not flippable in 2018. It just isn't.
