I would say two things:
First, the “progressive” (aka, “liberal” rebranded ) movement has a failed political outlook.
For Class Politics it has substituted Identity Politics (aka, the New Bigotry or the New Racism) and for Anti-Imperialism it has substituted “Humanitarian Imperialism.” Thus the bedrock issues of the genuine Left for almost two centuries have been jettisoned, and anyone from Hillary Clinton to Bernie Sanders to Amy Goodman can quite rightly call themselves “progressive” – and they do. Until this progressive politics is abandoned, there will be no Left let alone a successful Left. So when it is said that there is virtually no Left in the US any longer, that does not simply mean that progressives are ineffective; it means that progressives are not a genuine Left.
Second, it is also necessary to construct an anti-war, anti-Empire movement that is a single issue movement. This has been the key to the Pro-Choice and Gay Rights movements. And in practice it means that the Left will be working with very non-Left movements, from progressives of many stripes to the Anti-Empire Trump supporters. Whether the Anti-Empire movement will ultimately be led by Left or Right remains to be seen. But the progressives have screwed it up royally. And I would agree with the late, great Alex Cockburn that the efforts to build a Left/Right coalition against War and Empire have foundered on the unwillingness of most progressives to work with their brothers and sisters who have a conservative or libertarian outlook. On this score, when Trump turned his back on anti-interventionist policies, many [current pseudo] progressives finally found something for which they could love him, whereas many Trump supporters criticized him and many have already abandoned him. What does that say? Look at the “progressive” Rachel Maddow who is racking up ratings by peddling RussiaGate night after night with the wildest conspiracy theories. Certainly she is guilty of a terrible crime. But exactly who tunes in every night to drool over her rants and press on with RussiaGate which has probably already done in the New Detente, as Stephen F. Cohen likes to call it?
Perhaps the Left should begin by taking off the “soiled shirt” and cease calling ourselves progressives.