That means non-voters.
And who do German non-voters vote for? Die Partei, of course.
Twelve straight years of Angela Merkel have left politics feeling a little dry for young people in Germany. But now a satirical party is experiencing a surge in popularity after it was set up as a joke at the expense of the old system…
In the last few months the party has seen its membership swell to reach more than 25,000, just shy of the 26,000 members of the rising and much-publicised extreme-right party Alternative fur Deutschland (AfD), which is expected to enter parliament for the first time this year.
Nichtwähler wählen: Die Partei.

Perhaps your younger readers should know that “Die Partei” was the song/hymn of the KPD/ML communist party in East Germany : Hear it here :- https://www.youtube.com/watch?v=865Sn8JrMvY
Maybe they read it like it´s “The Party” and they want to cry if they want to!