Support for the death penalty has dipped to its lowest level in 40 years in the United States, a Pew Research Center reveals, though a small majority of Americans still believe in capital punishment, Time reported.

Fifty-six percent of the U.S. citizens surveyed said they backed executions -- a decline of about 6 percentage points during the past four years. During the 1980s and 1990s, surveys often found overwhelming support of 70 percent or more, the magazine noted.

"Much of the decline in support over the past two decades has come among Democrats," Pew's report pointed out. "Currently, just 40 (percent) of Democrats favor the death penalty."

Among Republicans, 77 percent say they back capital punishment, a decline of 10 percentage points from 1996, the pollsters revealed. They noted a similarly telling shift among independents, 79 percent of whom supported the death penalty in the mid-1990s -- a number that is now down to 57 percent.

Beyond party preferences, the Pew Research Center found that their demographics are an important key to Americans' feelings toward the issue: While 63 percent of whites favor the death penalty, for example, only 34 percent of blacks do, too; Hispanics fall in the middle: 45 percent of them agree with capital punishment.

Fifty-seven percent of individuals who are not religiously affiliated back the death penalty, and that support -- perhaps surprisingly -- rises further among white evangelical Protestants (71 percent) and white mainline Protestants (66 percent).

Sixty-three percent of white Catholics also speak out in favor, even though Pope John Paul II in 1999 appealed for a consensus to end the "cruel and unnecessary" practice and the U.S. Conference of Catholic Bishops has said that one should not choose "to end a human life in response to violent crimes if non-lethal options are available."

The parents of the youngest victim of the Boston Marathon bombings, meanwhile, have urged prosecutors not to pursue the death penalty for the man convicted in the case, CBS News reported.

Bill and Denise Richard, whose 8-year-old son, Martin, was killed in the April 2013 attack, told the Boston Globe that condemning Dzhokhar Tsarnaev to death "could bring years of appeals and prolong reliving the most painful day of our lives."