It’s a bit incredible it’s taken so long for the left to realize its demise, but I think most of its activists do understand. The problem for the average Dem voter is that they are fed fantasies by their politicians and the media. The root problem is that progressives are always trying to push a change agenda on a traditional society that adapts on its own time schedule. Obama’s unique presidency as the first non-white POTUS merely obscured this reality with fantasies of Hope and Change. He pushed and the people pushed back. The result was to weaken the Dem brand to its lowest point across the nation since before FDR. This was easily foreseen. The US population is center-right, not democratic socialist left.
But the left in the US has been in decline since 1972, or maybe 1968 when the DNC in Chicago blew up the party. How can a party unify around tribal identity politics where race, ethnicity, and gender count for more than universal moral principles? (See Jon Haidt for research on ideological moral priorities.) Only by forcing an unnatural coalition every 2 years. This means the Dem party is always on the precarious edge of disasters like GWB and Donald Trump.
Ironically, with his Marxist class tendencies, Bernie Sanders has been trying to push the party back to stronger class-based partisanship instead of failed identity group coalitions. But he gets attacked by the establishment Dems who thrive off identity group political activism and also realize socialism is a bit too radical for traditional American politics. So the left needs a revolution, but nobody in America wants a revolution.
A bad decade? Brace for the future because the Dem coalition must be destroyed before it can be rebuilt. The ultimate irony: they need a Trump.