Economist logic: 1) Obama championed Obamacare 2) Republicans hate Obamacare 3) Therefore Democrats are vulnerable Oh hey! What's this? A poll from yesterday with obamacare approval at 64% and climbing? Could it happen? Sure. Could it happen for reasons The Economist lists? That presumes the Economist has the first clue what they're talking about.
Presumes that the candidates (and politics) they swept out are facing a reckoning. As much as the Republican party wishes to believe it's relevant, it's not. Local races are going to be local. Nationally, the Republican party is somewhere south of the Zetas cartel, popularity-wise.
I hope hope hope so. Local races seem sort of random. Democratic districts will swing Republican if the rep in question has recently scored some federal blocks, and vice versa. Six seats isn't a huge number to make up. My guess is they'll miss taking it by inches. But anything could happen in the next six months.