Authorities investigate a truck after it plowed through Bastille Day revelers in the French resort city of Nice, France, on Thursday. (Sasha Goldsmith/AP)

Republican Donald Trump’s and Democrat Hillary Clinton’s efforts to portray themselves as assertive adversaries of the Islamic State terror group are increasingly defining the 2016 presidential race — and never more so than in the wake of the massacre in Nice, France, this week.

Although authorities have not yet tied the attack to jihadist-inspired terrorism, both candidates immediately responded to the latest in a string of attacks at home and abroad that have heightened voter anxiety by vowing aggressive efforts to combat the Islamic State.

They have done so in strikingly different ways, she with specific proposals and he with broad promises. But together, their messages effectively assure a war-time posture in the White House next year no matter who becomes president — and they mark a sharp departure on the campaign trail from the non-interventionist sentiment that then-Sen. Barack Obama rode into office eight years ago.

The intense jockeying was encapsulated in a round of dueling telephone interviews Thursday evening with Fox News host Bill O’Reilly, following the deadly truck attack in southeastern France that killed more than 80 people assembled to celebrate Bastille Day. The interview was especially notable for Clinton, who rarely speaks to Fox News but may have been trying to engage with conservative voters who care deeply about national security and may not be sold on Trump.

“We’ve got to do more to understand that this is a war against these terrorist groups, the radical jihadist groups,” Clinton said. “It’s a different kind of war. We need to be smart about how we wage it, but we have to be determined that we’re going to win it.”

Here's what the 2016 presidential candidates and other politicians had to say after a driver killed more than 80 people on Bastille Day in France. (Sarah Parnass/The Washington Post)

In his interview, Trump ticked through a list of recent attacks as evidence that a change in management style at the top is a necessity to blunt future attacks.

“You look at San Bernardino. You look at Paris. A hundred and thirty people killed and so many injured in Paris from that attack. And you look at Orlando. It’s out of control,” Trump said. “And Bill, unless we get strong and you know, really strong and very, very smart leadership, it’s only going to get worse.”

[In truck rampage, experts see potential shift toward cruder, deadlier acts of terror]

The back-to-back interviews underscored the differences in the two candidates’ approaches. Trump has embraced the debate over terrorism to emphasize his proposed ban on most foreign Muslims — which Clinton vigorously opposes — and advance a muscular but nebulous strategy to stamp out terrorists abroad.

Clinton has been more specific, arguing for a “smart” but strong effort to combat the Islamic State, focusing on ratcheting up intelligence cooperation between the United States and its allies and fighting radical propaganda online.

Clinton must walk a fine line. Even as she pursues centrist Republicans, including veterans of the Bush administration’s foreign policy shop, she is trying to consolidate support among Democrats after a bruising primary with Sen. Bernie Sanders of Vermont. Many liberals already see her as too hawkish, going back to her vote for the war in Iraq in 2002, which contributed heavily to her primary defeat six year later against Obama.

“There’s a lot of concern about another war in the Middle East,” conceded Sen. Jeff Merkley (D-Ore.), a Sanders endorser who helped the candidate win a landslide in his own state’s primary. “But look, this is not a choice between Hillary Clinton and Gandhi. This is a choice between Hillary Clinton and Donald Trump, and I’d be far more terrified of Trump’s reckless foreign policy than of Hillary Clinton.”

Trump faces challenges of his own. While his freewheeling rhetoric and his controversial Muslim ban and proposed wall along the Mexican border were big hits in the Republican primary, they have exposed him to accusations in the general election that he is not serious and ill-prepared for the rigors of major security decisions.

With the Republican and Democratic conventions taking place over the next two weeks, Clinton and Trump will be auditioning on the national stage at a time when the public’s attention has been repeatedly directed to global terrorism threats.

“It’s an electorate that is profoundly insecure and unsure about what happens next both in terms of the economy and increasingly in terms of international policy and terrorism,” said Anita Dunn, former White House communications director in the Obama administration. “Making the case to the American people that you are the person to address their issues and to make the country feel secure again is really the predominant challenge for both campaigns.”

[Assailant was ‘entirely unknown’ to anti-terror units, prosecutor says]

In his Fox News interview, Trump said he would ask Congress for a war declaration on the Islamic State, a move rarely used in American history.

“If you look at it, this is war coming from all different parts. And frankly it’s war, and we’re dealing with people without uniforms,” Trump said.

In her interview, Clinton used similar language to describe the threat posed by the Islamic State. But asked on CNN whether she would endorse Trump’s proposal to seek authorization from Congress for war, she made clear that she has no intention of drawing U.S. or NATO troops into a fight with the Islamic State. She called it the Islamic State’s “dream” to pull U.S. ground troops into a war in the region.

“I would point people to read more about what the hopes and ambitions of ISIS happen to be,” Clinton said, using a common acronym for the group. “They would love to draw the United States into a ground war in Syria.”

“They actually think the end times could be hastened if we had some great confrontation in that region,” she added.

Hours after the coup attempt in Turkey, Clinton became the first candidate to issue a statement calling for calm and “respect for laws, institutions, and basic human rights and freedoms.” The sentiment closely echoed the comments of Obama and Secretary of State John F. Kerry and offered an implicit contrast with Trump, who had not yet commented on the situation.

Still, Clinton has not shied away from supporting an aggressive and frontal approach to the threat.

She has argued that the United States and its allies should continue to reclaim territory from the Islamic State, boxing their fighters into smaller and smaller territory. She has criticized allies in the region for not doing enough to stop radicalization within their own borders, and she called on countries including Saudi Arabia and Qatar to invest more in the global effort to fight the Islamic State.

She has also embraced the language of more conservative politicians. After the Orlando attack on a gay nightclub by a self-radicalized convert to the Islamic State, Clinton said “radical jihadist terrorism” and “radical Islamist terrorism” are virtually the same, after once refusing to use the word Islam in the context of terrorism out of concern that it would only embolden the enemy and enable recruitment.

Trump, like many Republicans, has repeatedly slammed Obama for refusing to use the term “radical Islamic terrorism.” And he has accused Clinton of moving closer to his point of view.

In fact, Clinton’s positions are not that divergent from the policies of the current White House. Her hawkishness has been mostly displayed through rhetoric, or by degree — though she has strayed from the president on a key issue, stating that the Islamic State threat cannot be “contained,” as Obama has stated, but rather must be “defeated.”

Liberal Democrats who support Clinton have struggled to get Sanders supporters past her foreign policy record. At Netroots Nation, the annual conference of progressives held this year in St. Louis, Clinton’s campaign was nearly invisible. Foreign policy, a focus of some past conferences, was discussed only at a few crowded panels.

Rania Khalek, 30, a journalist who has written critically of Clinton, said the Democrat poses a more direct threat to the Muslim world than Trump.

“People are not going to protest when she decides to put boots on the ground in Syria,” Khalek said. “People are not going to protest when she decides to give Israel more military aid. She has a record of killing people. Donald Trump doesn’t have that record, yet.”

Jennifer Miller-Smith, a 50-year old Clinton supporter from Florida, argued that some progressives subjected Clinton to tests they never demanded of Kerry or Vice President Biden — for example, their support for the Iraq War.

“Iraq was a long time ago, and she’s learned since then,” Miller-Smith said. “We’ve all learned since then.”

“Even I believed Colin Powell,” she said about the former secretary of state.

Charles Khan, 28, a financial reform activist who was in seventh grade at the start of the Iraq War, said that polling and politics might curb Clinton’s hawkish tendencies.

“I think Hillary is smart and doesn’t want to do anything that is unpopular,” Khan said. “With a huge majority of Americans not wanting to be involved in another war, that’s probably the stance she’d take.”

Weigel reported from St. Louis.