Republicans continue to largely favour its use
The share of Americans who support the death penalty for people convicted of murder is now at its lowest point in more than four decades.
Only about half of Americans (49%) now favour the death penalty, while 42% oppose it.
Research from the Pew Research Center finds support has dropped seven percentage points since March 2015, from 56%.
It says public support for capital punishment there peaked in the mid-1990s, when eight-in-ten Americans (80% in 1994) favoured the death penalty and fewer than two-in-ten were opposed (16%).
Opposition to the death penalty is now the highest it has been since 1972, it says.
The survey of 1,201 adults finds that most Republicans continue to largely favour its use in cases of murder, while most Democrats oppose it.
By more than two-to-one, more Republicans (72%) than Democrats (34%) currently favour the penalty.
But while even as support has declined across nearly all groups, differences remain.
Men are more likely to back the use of the death penalty (55%) than women (43%), white Americans are more supportive (57%) than blacks (29%) and Hispanics (36%) - and attitudes on the issue also differ by age, education and along religious lines.
The research finds there are only modest difference by age and education in support for the penalty, with 18 to 29-year-olds somewhat less likely to support it (42% in favour) than those in older age groups (51% of those 30 and older).
Those without a college degree are more likely than those with at least a college degree to favour its use in cases of murder (51% vs. 43%).
Amnesty International say 18 US states, plus the District of Columbia, have abolished the death penalty - and seven more have not carried out an execution in at least 10 years.