The massacre in San Bernardino, now being investigated as a terrorist attack, has reshaped the political debate in an election year that strategists in both parties had thought would be fought out primarily over domestic policy.

“People want strength,� Donald Trump declared at a rally in Iowa on Saturday.

That imperative was powerful enough to push President Obama into giving his first Oval Office address to the nation in five years Sunday night. And in both parties, the candidates who hope to succeed Obama have scrambled to recalibrate their positions, seeking to respond to fearful, anxious voters.

Both sides face one central problem: The nature of the San Bernardino attack defies the solutions that either has been offering.

Because the attack does not appear to have been centrally directed or planned, a more intense assault on Islamic State’s positions in Iraq and Syria, as Republicans have advocated in recent months, might have little impact on preventing recurrences.

And because the attackers purchased their weapons legally after going through the required background checks, the preferred Democratic response of expanding the background-check system to cover additional sales has little relevance.

Both sides have offered some proposals for tightening the process for getting a visa to enter the U.S., an idea Obama alluded to in his Oval Office speech. And Democrats have pushed to ban gun purchases by people on terrorism watch lists.

President Obama will address the nation from the Oval Office on Sunday evening -- standing at a podium -- where he'll discuss his strategy for keeping Americans safe and for defeating Islamic State. As he speaks to the nation, Republican presidential front-runner Donald Trump will offer his own analysis on Twitter. On Sunday, Trump assailed Obama for what he said was the president's inability to keep Americans safe.

Republicans and Democrats running for president can't even agree how to describe the apparent motivation of the couple who killed 14 people last week in San Bernardino.

“Radical Islamic terrorism,� former Florida Gov. Jeb Bush, a Republican, said Sunday on ABC's "This Week."

“The left has a hard time recognizing what it is,� he said.

GOP presidential frontrunner Donald Trump agreed that “radical Islamic terrorism� is to blame.

“We have a president that won't issue the term. He won't talk about it. So, we're having this tremendous radical Islamic terrorism. OK? A lot of people don't want to even say it,� Trump said on Sunday.

The White House avoids using the phrase in part because it seeks to avoid alienating the world's Muslims, including leaders of crucial allies in the Middle East and millions of Americans who are Muslims.

Democrats tend to agree.

Hillary Clinton, the frontrunner for the Democratic presidential nomination, said Sunday she doesn’t use the phrase because it “sounds like we are declaring war against a religion."

"It doesn't do justice to the vast number of Muslims in our country and around the world who are peaceful people," Clinton said on ABC's "This Week."

At last month’s Democratic debate in Iowa, Clinton, along with Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O’Malley, all declined to use the phrase “radical Islamic terrorism.�

“Let’s not fall into the trap of thinking our Muslim neighbors and friends are our enemies,� O’Malley said. “We are going to defeat [Islamic State] there and around the world because Muslim Americans in our country and around the world are going to see [the group] is perverting the name of a great religion.�

He added, “calling it what it is is to say radical jihadists.�

Donald Trump has assailed Democrats and Republicans alike in his quest for the White House -- electrifying a GOP base yearning for a political outsider -- and on Sunday he attacked President Obama's efforts to combat acts of terrorism like last week's mass shooting in San Bernardino.

“Until he admits that this is a problem, we're never going to solve the problem,� Trump said on CBS’ “Face the Nation.� “But he's only going to be there, fortunately, a little bit more than a year. Because the problem will get solved when he gets the hell out.�

Trump remains the front-runner in the packed Republican field two months before voters in Iowa begin the nominating process.

He hammered Obama for his refusal to blame “radical Islamic terrorism� for the Islamic State attacks in Paris that killed 130 people last month, and the Dec. 2 massacre in San Bernardino that left 14 dead.

The White House avoids using the phrase in part because right-wing extremism has caused more deaths in the United States since 2001 than Muslim extremism, and partly because it seeks to avoid alienating the world's Muslims, including leaders of crucial allies in the Middle East.

Obama is scheduled to deliver a prime-time television address Sunday night to explain his strategy for keeping Americans safe and for defeating Islamic State.

Since the terrorist attacks in Paris last month, Trump’s campaign has focused largely on concerns about national security although he’s offered mostly vague details as to how to combat Islamic State.

Trump has made headlines in his vows to close mosques and create a database to register Muslims in the United States. On Sunday, he said the idea of profiling is valid considering the recent terrorist attacks.

“I think there can be profiling,� he said on “Face the Nation.� “If they thought there was something wrong with that group and they saw what was happening, and they didn't want to call the police because they didn't want to be profiling, I think that's pretty bad. People are dead. A lot of people are dead right now. So everybody wants to be politically correct, and that's part of the problem that we have with our country.�

Trump’s comments have been rebuked by some of his GOP challengers.

New Jersey Gov. Chris Christie, also appearing on “Face the Nation,� said profiling of American Muslims is not needed.

"The fact is we don't need to be profiling in order to be able to get the job done here,� said Christie, who is polling toward the bottom of the crowded field of candidates. “What you need is a president who's had the experience and the know-how to do this and not someone who's just going to talk off the top of their head.�

Former Florida Gov. Jeb Bush also rejected the need to profile.

“The director of the FBI has made it clear that there are hundreds of cases that they're monitoring, and we should redouble our efforts in that regard,� Bush said on ABC’s “This Week.� “We don't have to target the religion.�

President Obama on Sunday will take the unusual step of addressing the nation from the Oval Office to discuss his administration's counter-terrorism policies in the wake of the massacre in San Bernardino.

The FBI is investigating the shooting rampage, which killed 14 people, as an act of terrorism after officials discovered that one of the shooters pledged allegiance to the extremist group Islamic State just before the opening fire.

The White House said in a statement that Obama would discuss progress in the San Bernardino investigation and "the broader threat of terrorism — including the nature of the threat, how it has evolved and how we will defeat it."

"He will reiterate his firm conviction that ISIL will be destroyed and that the United States must draw upon our values — our unwavering commitment to justice, equality and freedom — to prevail over terrorist groups that use violence to advance a destructive ideology," the White House said, using an alternate name for Islamic State.