Lesser of two evils principle

The lesser of two evils principle, also referred to as the lesser evil principle and lesser-evilism, is the ethical principle that, when faced with selecting from two immoral options, the less immoral one should be chosen. The principle is most often invoked in reference to lesser evil voting, a binary political choice under systems that make it impossible to express a sincere preference for one's favorite.

Source: Wikipedia — Lesser of two evils principle (CC BY-SA 4.0)