This civil war has actually been going on for quite some time.  Bernstein seems only to note it because the credibility of the progressive dominated media is being seriously challenged.
And it will continue.  The left intends to create a one party state through government dependency, hence their attempt to foster the need for dependency by keeping the border porous to keep downward pressure on wages, and supporting their corporate multinational campaign contributors in moving good paying jobs to dictatorships with subjugate labor.  If Trump succeeds in bringing back good paying jobs their ideology will be discredited, so they cannot let him succeed.