Ten Democrats debated on-stage in Detroit, and it was the socialists vs. the moderates. Democrats being who they are, the moderates were the Washington Generals to the socialists' Globe Trotters. That is, their role was to be a foil for the night's heroes - Sanders and Warren.
Somewhere in musing about what is happening to Democrats, I had an epiphany which I will share with you. Democrats are desperate to defeat Donald Trump, who is doing a good job of President while producing more than his share of stylistic irregularities.
To give people a reason to vote D instead of R, Democrats have to say they will do things quite differently than Trump has. Stylistic differences alone, while taken for granted, won't cut it. Democrats feel (probably correctly) they have to advocate substantial programmatic changes.
Moderate Democrats' policies aren't enough different from Trump policies to make switching horses in midstream a big deal. Socialist policies are truly different, a decided break from Trump policies. Given this, moderate Democrats have trouble getting support from the party's energized base.
That base would like to see the U.S. move in the direction of European social welfare state policies: high taxes to pay for extensive benefits including comprehensive health care, state child care and free education through grad school. Such would not be my preferred outcome.
On the other hand, a radical give-away program of the sort Warren and Sanders advocate, may not pass muster with the people who elected Trump in 2016, or with independents. Joe Biden counts on that being a shared perception.
Sometimes parties are pragmatic and go for electability, sometimes they follow their heart and go for ideological purity. In extreme cases they nominate a hopeless McGovern or Goldwater. It remains to be seen which 2020 Democrats will do.