Hillary Clinton has cast herself as the most qualified to combat terrorism in the US after a weekend of violent attacks in three states.
Going after rival Donald Trump, she argued that his anti-Muslim rhetoric is helping Islamic militants, including the so called Islamic State (IS), recruit new fighters.
The Democratic presidential candidate touted her national security credentials at a hastily arranged news conference outside her campaign plane, accusing Republican Mr Trump for using the incidents to make "some kind of demagogic point".
"I'm the only candidate in this race who's been part of the hard decisions to take terrorists off the battlefield," Mrs Clinton, a former secretary of state, told reporters.
"I have sat at that table in the Situation Room."
She added: "I know how to do this."
New York's governor and mayor said on Monday that the bombings in a Manhattan neighbourhood and a New Jersey shore town are looking increasingly like acts of terrorism with a foreign connection.
Authorities are also investigating the stabbings of nine people at a Minnesota mall as a possible act of terrorism.
An Afghan immigrant wanted for questioning in the bombings was captured in New Jersey on Monday after being wounded in a gun battle with police, authorities said.
The violence cast a long shadow over the presidential race, diverting both candidates' attention from the daily controversies of the presidential race.
Mrs Clinton and her team see her foreign policy experience as a key selling point for her candidacy.
On the campaign trail, she frequently invokes her role in the 2011 raid that killed Osama bin Laden, describing to voters the tense atmosphere in the White House alongside President Barack Obama.
But while much of the foreign policy establishment has rallied around Mrs Clinton, Mr Trump's anti-immigrant rhetoric, promises to close US borders and vows to aggressively profile potential terrorists have fuelled his presidential bid.
"Knock the hell out of 'em," Mr Trump told Fox And Friends in a phone interview on Monday morning.
"We're not knocking them, we're hitting them once in a while; we're hitting them in certain places. We're being very gentle about it. We're going to have to be very tough," Mr Trump told Fox News Channel.
He said that US leaders, including Mr Obama, "coddle" potential terrorists.
Mr Trump once again took credit for predicting current events, pointing to his Saturday night announcement that a bomb had caused the explosion in New York City.
That was less than an hour after the explosion and before authorities had publicly said so.
Mrs Clinton urged voters not to "get diverted and distracted by the kind of campaign rhetoric we hear from the other side".
She insinuated that Islamic militants, particularly those affiliated with IS, are rooting for Mr Trump to win the White House.
The Republican has said he would bar immigration from nations with ties to terrorism.
"We're going after the bad guys and we're going to get them, but we're not going to go after an entire religion," Mrs Clinton said.
She briefly turned her focus from national security on Monday, wooing younger voters at a midday rally at a Philadelphia university.
Her campaign acknowledges she needs to do more to get millennials on board.
She is scheduled to meet with the leaders of Egypt, Ukraine and Japan late in the day in New York City.
The leaders are in New York for the UN General Assembly.
Mr Trump, too, announced plans to meet with Egyptian president Abdel-Fattah El-Sisi on Monday.
The events came as both candidates were dealing with missteps. Mr Trump and his allies spent Sunday - repeatedly and falsely - accusing Mrs Clinton of pushing the idea that Mr Obama was not born in the US - a conspiracy theory long championed by Mr Trump himself.
Mrs Clinton, meanwhile, is still facing questions about her health and openness after a video caught her staggering after abruptly leaving a 9/11 ceremony.