  Research on growing American political polarization and antipathy primarily
studies public institutions and political processes, ignoring private effects
including strained family ties. Using anonymized smartphone-location data and
precinct-level voting, we show that Thanksgiving dinners attended by
opposing-party precinct residents were 30-50 minutes shorter than same-party
dinners. This decline from a mean of 257 minutes survives extensive spatial and
demographic controls. Dinner reductions in 2016 tripled for travelers from
media markets with heavy political advertising --- an effect not observed in
2015 --- implying a relationship to election-related behavior. Effects appear
asymmetric: while fewer Democratic-precinct residents traveled in 2016 than
2015, political differences shortened Thanksgiving dinners more among
Republican-precinct residents. Nationwide, 34 million person-hours of
cross-partisan Thanksgiving discourse were lost in 2016 to partisan effects.
