Against the next war
Definitely the bumper sticker of the day:
Being against the next war requires some advance planning. Including but not limited to: voting for candidates who view out-of-control military spending as a dangerous waste, who foster international relationships even with our enemies, who work to understand other cultures, who can recognize and admit that we aren’t the greatest in everything, and who generally view US foreign policy with a critical eye.
If such candidates are not available, then vote for the ones nearest to that model, or against the ones farthest from it. Above all keep nationalist chest-thumpers away from the reins of power.