WASHINGTON — President Trump’s plan to use the death penalty on drug dealers has all the hallmarks of his favorite policies: It could fit on the front of a baseball cap. It is a proven applause line. It appeals to a conservative base.

But, like so many of Trump’s slogans-turned-policy, it’s dredged from a bygone era and lacks clear evidence showing it would be effective.

Using an obscure federal provision to bring capital cases against dealers, ­the concept that Trump enthusiastically backed during a visit to New Hampshire this week, fits within the framework of some of his other cornerstone ideas: Build the wall, Launch trade wars, Arm teachers. To some critics in the mainstream, though, the ideas are impractical, imprecise, or just dangerous.

“It’s a really baffling strategy. It’s taking us back decades, and without the benefit of all the data we’ve gathered since then,’’ said Brett L. Tolman, a former US attorney for the District of Utah, who prosecuted drug cases. “It’s almost jaw dropping that this discussion is even happening right now.’’

The proposal to impose the death penalty on drug dealers also serves as a dog whistle to the white nationalists who support Trump, according to critics, similar to strategies followed by governors with shaky records on race. These include former Alabama governor George Wallace, who backed the death penalty idea in 1985, and the current governor of Maine, Paul LePage, a Republican who blamed minorities for the drug problems in the state, at one point saying “Black people come up the highway and they kill Mainers.’’

“Unless you have really, really powerful penalties, led by the death penalty for the really bad pushers and abusers, we are going to get nowhere,’’ Trump said in Manchester, N.H., on Monday. “And I’m telling you, we are going to get somewhere.’’

The president said Lawrence and Boston — cities with large numbers of minority residents — are havens for dealers who ship drugs to New Hampshire. And he added: “If we’re not going to get tough on the drug dealers who kill thousands of people and destroy so many people’s lives, we are just doing the wrong thing. We have got to get tough. This isn’t about nice anymore.’’

Trump says that he’s drawn inspiration for his push to execute drug dealers from unspecified foreign leaders, and in the past he’s praised President Rodrigo Duterte of the Philippines for his handling of the country’s drug epidemic, a program that’s involved extrajudicial killings of both drug dealers and drug users.

He’s also praised the drug laws in Singapore, where drug dealing carries a mandatory death sentence in most cases. Trump has accepted an invitation to meet Prime Minister Lee Hsien Loong in Singapore later this year.

“This is tough on crime to the extreme,’’ said Kristen Clarke, president and executive director of the Lawyers’ Committee for Civil Rights Under Law, a Washington-based advocacy group that works to expose legal inequities for minorities. “This runs contrary to our approach to criminal justice reform. The president has used racially charged rhetoric in talking about drug offenses in the county. . . . And in that context it appears blacks and Latinos would be the ones impacted by such an outrageous proposal.’’

It’s unclear exactly how Trump wants to apply the federal death penalty statute. Under current law, the federal government can punish some drug dealers with death even if their activity isn’t directly linked to a fatal overdose, according to Robert Dunham, the executive director of the Death Penalty Information Center.

The federal power that Trump would use for his plan comes from a death penalty expansion provision that became law as a part of a 1994 crime bill. The legislation, which also banned assault weapons, gained support from a number of Democrats. They include then Senators Joe Biden, Edward Kennedy, and John Kerry. And, in the House at the time, Bernie Sanders, now a Senator from Vermont and darling of the left, voted for it.

President Bill Clinton signed the overall package into law despite constitutional concerns about the death penalty provisions, Dunham said. And, he said, the statute wasn’t used in part because of those concerns.

The law became even more questionable in eyes of prosecutors in 2008 when the Supreme Court determined, in a case of child rape, that the death penalty could not be imposed. That opinion had a chilling effect on using the death penalty for criminals who weren’t convicted of murder.

That means any cases that Attorney General Jeff Sessions might bring under the untested federal authority would almost certainly be appealed all the way up to the Supreme Court, prosecutors said.

A spokeswoman for Sessions confirmed the Department of Justice has the power to bring death penalty cases against drug lords, but declined to answer any questions about what type of cases would be pursued.

Trump’s concept would also be a major shift in how federal death penalty cases are brought, as most capital cases are prosecuted on the state level. Of the roughly 2,800 prisoners on death row, just 61 of them were convicted in the federal system as of July 2017, according to the Death Penalty Information Center. The federal government has executed just three people since 1976, according to the center’s data.

Florida is the one state in the country that also allows capital punishment for drug dealers, according to the National Conference on State Legislatures, which tracks state laws.

Another concern about widespread use of the death penalty is that federal prosecutors have a long history of increasing charges against even low-level drug users, making them at times appear to be much more powerful than they are, said Tolman, the former US attorney from Utah.

He recalled securing a lengthy prison sentence for a man he successfully prosecuted for distributing methamphetamine, even though the man had only what he described as a “Snickers bar’’ amount of the drug.

“We were able to show this was a distributable amount,’’ Tolman said. “That guy was put down as a major meth dealer. He was just a user who would get his score and give some to his buddies. That is the bulk of who is in the federal system. That is a dirty secret.’’

Adding the death penalty, he predicted, would only make the justice process longer and more expensive.

The idea of killing drug dealers, however, has been pleasing certain crowds for decades. President Ronald Reagan turned to Southern governors in 1985, asking for possible solutions to the outbreak of illegal drugs in the country at the time.

Death was the answer, one of the governors said.

“Anyone bringing in a DC-6 load of marijuana or cocaine is probably going to result in several deaths,’’ said George Wallace, who was then the Democratic governor of Alabama, according to the Miami Herald from the time. “You execute a few of them, and that would be the end of it.’’

Annie Linskey can be reached at annie.linskey@globe.com. Follow her on Twitter @annielinskey.