Gallup has measured Americans’ beliefs about the moral acceptability of the death penalty and numerous other social issues each May since 2001.

This year, 40% of U.S. adults think the death penalty is morally wrong, the highest in Gallup’s 20-year trend. The high point in the public’s belief that the death penalty is morally acceptable, 71%, was in 2006. That year and again in 2007, it topped the list of issues rated for moral acceptability.

The latest decrease in the public’s tolerance for the death penalty is largely owed to political liberals and moderates. While two-thirds of conservatives still consider it to be morally acceptable, moderates (56%) and liberals (37%) are at their lowest levels since 2001.