One reason Donald Trump can profit from his rabid fear-mongering is because there’s no one out there to calm the nation down.

According to a new New York Times/CBS News poll, Americans are more fearful about the likelihood of another terrorist attack than at any time since right after 9/11. A plurality of the public views the terrorist threat as the top issue facing the country.

Americans need a leader they trust who can assure them that everything possible is being done to secure the country. Obviously, that leader should be President Obama, who meant to provide such assurances in his Oval Office address to the nation right after the San Bernardino shootings.

He did not succeed. That failure helps explain why a climate of panic is fueling the most ugly election season in decades.

According to the New York Times poll, 57 percent of Americans disapprove of Obama’s handling of terrorism and the threat from Islamic State, while seven in 10 say the fight against Islamic State is going badly. In other words, a rare Oval Office speech did little to calm America’s angst.

But here’s an important news bulletin: Americans don’t see Donald Trump as their savior, either. Despite Trump’s rising support among Republican primary voters, the Times poll shows that 64 percent of the broader electorate would be concerned or scared about what he would do as president.

This confirms my belief that most Americans have not lost their minds.

However, Obama’s inability to assuage the public’s legitimate fears creates continued openings for demagoguery in a vicious campaign season. His failure goes beyond the serious weakness in his policies for combating Islamic State.

After all, Trump has no policy except to “bomb the s— out of them (Islamic State).” Nor have his GOP rivals come up with much better (Ted Cruz’s answer is to “carpet-bomb them into oblivion”).

What’s needed now is a leader with the FDR touch, who can reassure Americans of their strengths and of his commitment to the fight, while pulling no punches. That reassurance was sadly lacking in the Oval Office speech. Obama chose to stand professorially behind a lectern — displaying his famous cool, lawyerly demeanor — rather than emulate the warmth of Roosevelt’s “fireside” radio chats.

Of course, a big part of Obama’s problem is that he is selling an incoherent plan. His speech merely tweaked a flailing Mideast policy and called for the public to be patient. “Our success won’t depend on tough talk,” the president said.

But he never explained why coalition air strikes in Syria and Iraq would work now, when they have proved inadequate so far; there is still no effective Sunni Arab fighting force on the ground to call in targets or take advantage of U.S. air power. Nor did Obama explain how sending 50, or 150, more U.S. Special Forces can remedy the lack of Sunni ground troops. (America’s Kurdish allies cannot and will not vanquish Islamic State on their own.)

Moreover, the president still rejects any criticism of his refusal to help Syrian moderate fighting groups in 2012 (when they existed) or to arm Iraqi Sunni tribesmen eager to fight Islamic State. This creates a gaping hole in his policy that the public grasps.

Instead, Obama and his team are betting that Vladimir Putin will endorse a U.N. peace plan, which ends the fighting in Syria, dumps President Bashar al-Assad, and unites the West, Russia, and the Syrian army to fight Islamic State. To put it kindly, this is a mirage.

So yes, the president’s failed policies stoke public anxieties. Americans don’t want to send tens of thousands of troops back to the Mideast (nor would a GOP president do so), but they do want a leader who seems to know what he is doing.

Yet I still believe that the source of America’s angst goes deeper than Obama’s foreign policy mistakes.

At a time of pervasive change, in both the economic and global realms, people want a leader who can convince them they’ll be safe. Right now, many Americans can’t identify that leader.

GOP candidates hardly fill the bill; Trump’s opponents have been whipping up some of the same hysteria over refugees and Syria with only slightly less fevered language. Hillary Clinton’s foreign policy speech in Washington last week had a strong, compassionate tone, but she is just laying out her foreign policy program. Bernie Sanders grasps the climate of public outrage but is no foreign policy wonk.

And Obama lacks the empathy to reassure the public (qualities that I believe would ameliorate some of the unease over his policies).

Feeling leaderless and rudderless, even some Americans who would normally reject a demagogue may succumb to the appeal of a strongman. As I have written before, I don’t think the Donald will make it to the White House. But I fear this election season will get even uglier — especially if domestic Islamic State wannabes exacerbate the confusion at home.

— Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.