Democrats have to campaign on something else besides a great economy, rising values of savings, low unemployment across every demographic, clarity about allies and enemies abroad, and a rebuilding military.
The economy is not great. The last quarters' GDP was mostly building inventories. That won't last. There are plenty of headwinds. They change constantly. Unemployment is still a factor of a low participation rate. Wages sure haven't rocketed up. As for rebuilding the military, what's great about that? The last thing we've needed is an arms race. Nothing wastes like the Pentagon. All that money and effort could be going into fixing crumbling infrastructure and other needed things. As for Israel, perhaps someone hasn't noticed just how many Americans (including many, many Jews) are speaking out against the clearly racist government of Netanyahu and his war crimes against Palestinians.
Hugh Hewitt, the author, also claims Sanders is "too liberal." Sanders was polling higher than Trump going into 2016. Watch what happens when the Democrats start the debates. Who's going to be running against Trump for the Republican nomination? He won't have the limelight. The Democratic nominee will have had it throughout the primary season. All of Bernie Sanders' programs are more popular than are Trumps, and the youth continue moving left, growing up, and becoming voters.