Hillary Rodham Clinton (D) says small towns are facing a “quiet epidemic” of drug use. (Melina Mara/The Washington Post)

When aspiring presidential candidates step into Mayor Ted Gatsas’s office here, he doesn’t let them leave without telling them about what he calls one of the most pressing, dire issues his city faces: heroin.

“Every candidate that comes in here, what I say to them is, ‘It’s not only an issue here in Manchester, New Hampshire. It’s a national issue,’ ” said Gatsas (R). “If we don’t get our arms around it, it’s going to take over our country.”

The nation is in the throes of an epidemic of prescription-drug and heroin abuse — a wave that’s leaving its mark on the 2016 presidential campaign, too.

Hillary Rodham Clinton has told supporters that drug abuse and mental health will be key issues in her Democratic presidential campaign, and she launched a policy-focused outreach effort on the issue. New Jersey Gov. Chris Christie (R) recently participated in a round-table discussion at a drug treatment facility here. Republican Carly Fiorina has spoken movingly about losing a stepdaughter to addiction. Sen. Rand Paul (R-Ky.) has made reforming drug laws and the criminal-justice system a centerpiece of his presidential campaign. And former Florida governor Jeb Bush (R) said he learned about New Hampshire’s heroin problem while touring as a potential presidential candidate.

Drug addiction and treatment are no longer problems acknowledged only with infrequent stump lines. They are driving a sustained conversation on the presidential campaign trail.

New Jersey Gov. Chris Christie (R) often speaks of a law-school classmate’s battle with addiction and his death of an overdose. (Julie Jacobson/AP)

And that conversation revolves around ending — not stepping up — the war on drugs. It centers on the language of addiction and treatment, on the sharing of deeply personal experiences and on calls from candidates for the criminal-justice system to be restructured to make the government’s response to illegal use less punitive.

It is being driven by voters such as Pamela Livengood of Keene, N.H., who told Clinton last month that she has had to take on the care of her grandson because of drug abuse.

“Grandpa and I have guardianship of him because of all the growing drug problem in our area that my grandson’s mother can’t be quite so responsible,” Livengood said carefully. “So we’ve picked it up and took over, but we also need to see more for substance abuse help in our area. There are very limited resources here.”

Clinton responded that she was “really concerned because, Pam, what you just told me and I’m hearing from a lot of different people.” She described drug use as a “hidden . . . quiet epidemic,” different from the headline-grabbing phenomenon of the 1980s, that is “striking in small towns and rural areas as much as any big city.”

According to the Centers for Disease Control and Prevention, the number of deaths nationwide involving heroin increased from 3,041 in 2008 to 8,260 in 2013, the most recent year for which statistics are available. In 2013, 16,235 people died from overdosing on prescription opiates; in 2008, 14,800 people died. Drug overdoses were the nation’s leading cause of injury death in 2013, according to the CDC. Among people 25 to 64, overdoses caused more deaths than traffic accidents.

Here in New Hampshire, the state’s medical examiner has called heroin abuse “the Ebola of Northern New England.” New Hampshire recorded 325 drug overdose deaths last year; about 90 percent of them involved opiates, according to the medical examiner’s office. The state also has seen a rapid increase in the number of deaths from the painkiller fentanyl, which is often mixed with heroin.

“I am not at all surprised that it’s coming up in community conversations around New Hampshire, because this is the community conversation that is happening in New Hampshire right now,” said Tym Rourke, chairman of the commission on alcohol and other drug abuse prevention set up by Gov. Maggie Hassan (D).

Christie held a roundtable discussion last month at the Farnum Center, a drug abuse treatment facility here and relayed a story he often tells, about how a law-school classmate struggled with an addiction to prescription painkillers. The friend died in a New Jersey hotel room with an empty vodka bottle and an empty painkiller bottle.

“This is a treatable problem,” Christie said. “And we need to start talking about it like an illness, not like some moral failure.”

On the same trip, the New Jersey governor discussed addiction at a Manchester pizza place that had recently experienced the death of an employee from a heroin overdose.

For years, Christie — a former prosecutor — has been advocating treatment over incarceration for low-level drug offenders, sometimes framing that approach as part of being “pro-life for the whole life.”

In response to a surge in opioid deaths in New Jersey, Christie signed a bill in April to establish a statewide task force. He has expanded drug courts and broadened access to naloxone, a drug that can reverse the effects of an opiate overdose.

Paul has made reforming drug laws one of the signature issues of his time in the Senate and in his presidential campaign, often telling audiences that the war on drugs has failed — that it has “created a culture of violence and put police in an impossible situation,” as he said in Las Vegas in April — and that low-level drug offenders should go into treatment rather than being jailed.

Carly Fiorina’s stepdaughter Lori Ann Fiorina died in 2009 at age 34 after struggling for years with alcohol and drug addiction. Hours after announcing her presidential bid last month, Fiorina said the country must change the way it deals with people who are addicted to drugs.

“Drug addiction shouldn’t be criminalized,” she said on a conference call. “We need to treat it appropriately.”

For all the talk, there’s little yet in the way of policy plans. The first votes of the 2016 campaign are still months away, and so far, no candidate has come up with concrete proposals on how he or she would handle the epidemic from the Oval Office.

Over the past week, Clinton’s campaign has started to move in that direction. Campaign advisers held Google hangouts with treatment providers, law enforcement officials and others in Iowa and New Hampshire, and Clinton asked voters to share their thoughts on and experiences with substance abuse with her in a Facebook chat. The campaign has said it will use the information to develop policy proposals.

Clinton herself has spoken about addiction numerous times in New Hampshire and brought it up at a campaign event in Iowa. The former U.S. secretary of state said she had heard all over Iowa about two issues: mental illness and drugs.

“The drug epidemic, meth, pills in Iowa — and then I got to New Hampshire and at my very first coffee shop meeting I heard about the heroin epidemic in New Hampshire,” Clinton said in Mason City, Iowa, last month. “This is tearing families apart, but it is below the surface. People aren’t talking about it, because it’s something that is hard to deal with.”

During a stop in Davenport, Iowa, on Saturday, Clinton rival Martin O’Malley was asked by two women in the audience about the issue. Both were wearing T-shirts with a photo showing one of the women’s sons, who had died of a heroin overdose.

“Sadly, many of us are becoming much more expert on the tragedy of heroin overdose deaths in our country because of what’s happened recently,” said O’Malley, the former Maryland governor, who hugged both women.

O’Malley sought, with limited success, to combat the issue during his tenure as governor, which ended in January. In 2014, 578 people in Maryland died of heroin overdoses, a 25 percent increase over 2013 and more than twice the number who died from using the drug in 2010.

One question Republican candidates will face — but which Clinton and O’Malley will not — is how they plan to cover addiction treatment if they want to repeal the Affordable Care Act. That law mandates that insurance plans make substance-abuse and mental-health treatment essential benefits.

But even under the ACA, treatment is often hard to come by, and barriers to access remain. A report issued last month by the National Alliance on Mental Illness suggested that some patients are still being denied care.

“The issue is, [candidates are] talking about it, but are they committed to making sure that adequate funding and services are available for these people?” said Dedric L. Doolin, senior deputy director of the Area Substance Abuse Council in Cedar Rapids, Iowa. Doolin wants candidates to ensure long-term treatment will be funded.

Here in Manchester, Gatsas, the mayor, said he is bringing together law enforcement officials, treatment providers and others to try to tackle the issue locally. But they will not be the only ones hearing from the mayor, who said he plans to continue to press the issue with current and prospective presidential candidates. He predicts that his constituents will, too.

Candidates now “hear it even more on the stump, because people want to know, ‘What are you going to do?’ ”

John Wagner in Iowa contributed to this report.