Final answer:
The eugenics movement started to waiver or flounder in the mid-twentieth century due to negative outcomes, ethical concerns, and a decline in support after the atrocities of World War II. Advancements in scientific understanding and a growing emphasis on human rights also contributed to its diminishing influence.
Step-by-step explanation:
The eugenics movement started to waiver or flounder in the United States in the mid-twentieth century, particularly after the atrocities committed by the Nazis during World War II were widely publicized. The negative outcomes and ethical concerns associated with eugenics, such as forced sterilization and discrimination against certain groups, became more evident, leading to a decline in support for the movement.
Additionally, advancements in scientific understanding and a growing emphasis on human rights contributed to the diminishing influence of eugenics.