In this case: creationism.
Source: National Geographic
In 2013 another survey asked, “Humans and other living things have evolved over time.” Only 43% of those who identified as Republicans agreed. This was down from 54% in 2009. An 11% decline in 4 years.
Among Democrats 67% answered true while 65% of Independents agreed. Pew’s researchers said party differences remained when other factors — such as the racial and ethnic composition of the political groups, and religious and educational background — were taken into account.
That's pretty bad, but it might explain why other silly beliefs have taken hold in US society.
See also:
Evolution Less Accepted in U.S. Than Other Western Countries, Study Finds