When nine mothers of tragically slain children walk on to a stage and talk about the legacy of their sons and daughters, it is deeply heartbreaking. When a woman stands behind a lectern and talks about how her son never should have died in Benghazi, it is moving to the point of discomfort. Another woman recites how many seconds it took for a gun to fire the bullets that killed her only child, and members of the audience are moved to tears.

Grieving mothers have been a constant presence at both political conventions this week; in an election cycle where the public has grown used to escalating rhetoric, grieving mothers are the nuclear option in the emotional arsenal.

In Cleveland, Patricia Smith wept as she told the Republican delegates and the world about not having the answers she wanted for the Benghazi attacks: “I blame Hillary Clinton personally for the death of my son,” she said.

In Philadelphia, Lucy McBath, whose 17-year-old was shot at a Jacksonville, Fla., gas station in 2012, told the Democrats: “You don't stop being a mom when your son dies.” She and her eight compatriots were there to advocate for other children, she said, “and Hillary Clinton isn’t afraid to say black lives matter.”

In Cleveland, Mary Mendoza and Sabine Durden talked about how their children were killed by vehicles driven by undocumented immigrants. In Philadelphia, Christine Leinonen talked about her son, who was killed in the Pulse nightclub shootings in Orlando.

Christine Leinonen's only child Christopher and his boyfriend Juan died in the Pulse nightclub shooting in June. She spoke at the Democratic convention, saying her son was "a big Hillary supporter." (The Washington Post)

“I’m glad common-sense gun policy was in place when Christopher was born,” the former state trooper said, talking about being asked to relinquish her firearm when she arrived at the hospital to deliver her son. “But where was that common sense the day he died?”

Donald Trump has made immigrant deportation a cornerstone of his campaign; Hillary Clinton has supported gun control legislation. These issues are now so divisive in America that the only way to claim a position of moral authority is to reinforce it with people whose lives have been destroyed by them.

And then, once that moral authority is staked out, other people will suggest that, although the emotions of these women are pure, they are being exploited for political gain. During the Democratic primaries, as both Clinton and Bernie Sanders met with the families of black victims of violence, a columnist from the Root labeled the practice the “Black Lives Matter endorsement primary . . . the rush from both team Clinton and team Sanders to secure the public support and endorsement of victims.”

After Patricia Smith spoke in Cleveland, a columnist from the Guardian cited some disputed narratives within her speech, concluding that she must have been overcome by grief. “But we don’t exploit it by putting a person in the grip of such horror on a national stage,” the columnist wrote.

“I was not exploited,” Smith said when reached at her California home the week after her speech. “I felt like I was finally able to open up my mouth and say how I feel, and have people listen to me.”

“Do you think this group of women could be coerced into doing something we didn’t want to do?” Lucy McBath said when reached in Philadelphia the day after her speech. “That we would immerse ourselves in a cause that in any way would hurt the legacy of our children?” McBath explained that she had been a longtime supporter and admirer of Clinton’s — that she felt “blessed and thankful” to have been called upon as a leading voice in a campaign she believed in and she felt honored to be on the stage.

It has been only a few decades that citizens would be invited to participate in a convention in this way. Before that, it was considered unseemly to blend the personal with the political.

Democrats in Philadelphia reflect on the significance of nominating Hillary Clinton for president – the first time a major party has nominated a woman for the nation's highest office. (Peter Stevenson,Alice Li,Sarah Parnass,Jayne Orenstein,Nikita Mandhani,Adriana Usero/The Washington Post)

The citizen’s stage began to open in the 1980s, when Ronald Reagan started inviting regular Americans to a special box at the State of the Union speech, said David Karol, a University of Maryland political scientist. In 1992 a mother named Elizabeth Glaser appeared at the Democratic National Convention in New York. She had gotten AIDS via a blood transfusion and, not knowing she was sick, passed it to her unborn children. “My daughter died,” she told the floor. “She did not survive the Reagan administration.”

But before that, long before that, we turned to grieving mothers because grief was one of the few acceptable ways for women to participate in the political system, said Heather Cox Richardson, a history professor at Boston College. Women were not supposed to speak on political issues unless they spoke from their role as mothers; it was the one perspective that men acknowledged they did not understand. Mothers argued against the slave trade, saying it was barbaric because it separated women from their babies. Mothers rallied against drunk driving. Mothers formed Mother’s Day, which was not originally a Hallmark holiday but a cry of protest post-Civil War: Mothers no longer wanted to send their sons to war because mothers were tired of them dying.

And now today, mother after grieving mother comes onto the political stage, talking to a country that is worried about its own children, deeply conflicted over its next parent in chief, and wondering who will keep their children safe.