This is their greatest weakness, the Marxist faith in the "iron laws of history". The armies of socialism only march in one direction.
From 1932-1978, US election results and this false fixed belief moved in tandem.
Since 1980, and especially since 1994, things haven't been so good.
This has caused all sorts of other, more absurd Marxist "theories" like false consciousness and economic determinism to bubble to the surface.
The fact is, they are losing this country after having it in their reach, and they are suffering from severe cognitive dissonance as a result.
After all, their victory is guaranteed by the "iron laws of history".
Marx was fixated on the economy and he forgot about the biology. Natural selection eliminates leftists (who abort their own children and indulge in the sexual orientations) very quickly. Each generation half of them dies out.