“The death penalty is kind of dying a slow death, because we aren’t executing people at the rate we used to,” said Bill Keller, the former top editor at the New York Times who now runs the nonprofit Marshall Project, which focuses on criminal justice issues. “Prosecutors don’t push for the death penalty as much (because) the appeals process drags on for so long.”

In calling for the abolition of the death penalty in the platform, Democrats are out in front of both public opinion and the leaders of their party.

Both Gallup and Pew polls last year showed a majority of Americans (56 percent in the Pew survey, 61 percent in Gallup’s) still support death sentences, although that is a marked decline from 1994, when 80 percent of Americans told Gallup they supported capital punishment.

And neither President Barack Obama nor Hillary Clinton have formally called for an end of the death penalty, though both have been critical about how it has been administered. Those positions are in some ways similar to the caution they exhibited before embracing same-sex marriage.