Norman J. Ornstein and Thomas E. Mann, at Vox:

As scholars who had worked for more than four decades with lawmakers on both sides of the aisle, we faced a ton of scorn from sitting Republican lawmakers and outside observers for making this argument — and denial from most of the mainstream media. For reporters, professional norms and concerns about accusations of partisan bias dictated that the parties be treated equally, whatever the underlying reality. The safe haven of false equivalence led the press to ignore one of the most consequential developments in contemporary American politics: the radicalization of the Republican Party.