Hillary Clinton threw a barrage of stinging one-liners at Donald Trump on Thursday. But at the heart of her speech was one powerful question for voters: “Do we want his finger anywhere near the button?”

In an address that slammed Trump on everything from what Clinton called his bigotry toward Muslims and Mexicans to his talk of torturing terrorists and executing their family members, nothing was so grave as Clinton's implication that a Trump presidency might end the 70-year global taboo against the use of nuclear weapons.


“This is not someone who should ever have the nuclear codes,” Clinton said. “It’s not hard to imagine Donald Trump leading us into a war just because somebody got under his very thin skin.”

At a time when Clinton is road-testing lines of attack against the businessman who sometimes seems immune to traditional political rhetoric, Democrats say the nuclear issue could be especially potent, touching on some of the deepest fears voters have about their own security.

Clinton is not the first to raise the question, however, and it remains to be seen whether she will succeed where Trump’s GOP rivals failed.

In Clinton’s telling, Trump isn't just temperamental and prone to impulsive fights—he's dangerously cavalier about nuclear weapons and their potential for death and destruction on a mind-warping scale.

"This is a man who said that more countries should have nuclear weapons, including Saudi Arabia," Clinton said.

Clinton also recalled Trump’s quip about a potential conflict between Japan and North Korea: “If they do, they do. Good luck, enjoy yourself, folks.”

“I wonder if he even realized he’s talking about nuclear war,” she marveled.

Clinton also reminded listeners that Trump “refused to rule out using nuclear weapons against ISIS, which would mean mass civilian casualties.”

The power of invoking nuclear weapons is well diminished from the terrifying heights of the Cold War, conceded Democratic pollster Jeremy Rosner, who recalled the infamous 1964 campaign ad Lyndon B. Johnson’s campaign ran against Barry Goldwater implying that his aggressive anti-communist policies might lead to nuclear conflict with the Soviet Union. In the ad, the image of a little girl plucking petals from a flower is suddenly replaced with a mushroom cloud in what became known as the “Daisy” ad.

But, Rosner said, the nuclear question is still among the simplest and most powerful ways to focus voter attention on a candidate’s fitness to be president.

“It’s an effective card,” Rosner said. “If you go back to 1964 and the Daisy ad, it’s a well-established idea that if someone is extreme the most dangerous manifestation of that is what they would do as commander in chief.”

There is some evidence to suggest that Clinton already has the better part of the argument. When Fox News asked voters in mid-May whom they trust more with “decisions about nuclear weapons,” the former first lady and secretary of state came out ahead of Trump by 11 points, 49-38.

Trump has said contradictory things about nuclear arms. During a December primary debate, he said the U.S. must be "extremely vigilant and extremely careful when it comes to nuclear," adding that "the biggest problem we have is nuclear proliferation, and having some maniac, having some madman go out and get a nuclear weapon."

More recently, Trump has seemed to shrug his shoulders at the idea that more countries might acquire nuclear arms in the near future, something he said in a CNN town hall in April "is going to happen anyway." He has even shown clear support for admitting certain new members to the nuclear club: “Wouldn't you rather in a certain sense have Japan have nuclear weapons when North Korea has nuclear weapons?” he asked during the CNN event. (Also at the forum, Trump flatly stated that he does not favor a nuclear-armed Saudi Arabia, contrary to Clinton's assertion Thursday.)

Clinton is hardly the first to fret in public about Trump's potential proximity to the nuclear "football," the briefcase carried by a military aide who travels with the president containing communications equipment that allows him to authorize a nuclear launch. Marco Rubio warned against handing “the nuclear codes of the United States to an erratic individual.” Jeb Bush said that he had “grave doubts” about entrusting Trump with America's atomic arsenal. And Louisiana Gov. Bobby Jindal fretted against entrusting "such a hothead with the nuclear codes."

Rosner added that the question of foreign conflict has more salience since the Iraq War, which has left swing voters "expressing a lot of worry about a Republican tendency to 'shoot from the hip' and not think through the use of force. That obviously goes far beyond nukes, and gets to fears of getting involved in another foreign war without clear purpose or outcome."

That fear has dogged Republicans for decades.

In 1980, aides to Ronald Reagan were sensitive to Democratic charges that their candidate, most famous for being a Hollywood actor and derided as a flake by his critics, might blunder into World War III. One memo from Reagan strategist Richard Wirthlin warned of voter fears that Reagan "would be too quick to push the nuclear button" and urged him to talk more about peace and safety.

"We must position the Governor, in these early stages, so that he is viewed as less dangerous in the foreign affairs area," Wirthlin wrote.

After Clinton's Thursday broadside, Donald Trump's aides may be thinking the same.