people don't respond very strongly to strangers' exhortations to get out and vote.

The shock is that anyone would be surprised by this.

This is the main reason that Republican GOTV now beats Democratic GOTV whenever it matters.  The Republicans have organized, mostly through churches, into what I call Amway Precincts.  They are networks of people who know each other, people who connect their respective social and family networks to the hub of the Amway Precinct and who turn out every election.  They do the latter because the Republicans reliably give them a simplistic thing that they care about that they can vote on:  gay marriage being the most famous example.

Democrats have not done this or even attempted to do so.  The meetups that were such a big part of the Dean campaign fell into disuse after that campaign's collapse.  The local and state Democratic Party officials do not want to build a network like this because they are threatened by it.