WASHINGTON(TIP): Under the shadow of overseas violence, Republican Donald Trump and Democrat Hillary Clinton padded their leads on Tuesday with victories in Arizona and attacked each other as the 2016 presidential contest turned into a clash over who could best deal with Islamic extremism.

Democratic challenger Bernie Sanders scored a win in Utah’s Democratic caucuses, claiming victory in the Western state as he tries to keep pace with Clinton who has a seemingly insurmountable lead in the delegate count. He netted some delegates in Utah, but not enough to make up for his loss to Clinton in Arizona.

Long lines and high interest marked primary elections across Arizona, Utah and Idaho that were largely an afterthought for much of the day as the world grappled with a new wave of bloody attacks in Europe. The Islamic State group claimed responsibility for blasts at the airport and a subway train in Brussels that left dozens dead and many more wounded.

“This is about not only selecting a president, but also selecting a commander-in-chief,” Clinton said in Seattle as she condemned Trump by name and denounced his embrace of torture and hardline rhetoric aimed at Muslims. “The last thing we need is leaders who incite more fear.”

Trump, in turn, branded Clinton as “Incompetent Hillary” in an interview with Fox News as he discussed her tenure as secretary of state. “Incompetent Hillary doesn’t know what she’s talking about,” the billionaire businessman said. “She doesn’t have a clue.”

The back and forth between the front-runners came amid a frenzy of activity from voters eager to make their voices heard in the 2016 election.

In Utah, caucus-goers were dispatched by poll workers to local stores with orders buy reams of paper and photocopy fresh ballots amid huge turnout. The state Democratic Party’s website crashed due to high traffic.

In Arizona, voters waited two hours or more in some places to cast primary ballots, while police were called to help control traffic.

The results from Arizona didn’t bode well for Democrat Bernie Sanders and Republicans Ted Cruz and John Kasich. They are running out of time to slow Trump and Clinton’s march toward acquiring all the delegates needed to claim their parties’ nominations at the parties’ national conventions in July.

Trump’s Arizona victory gives him all of the state’s 58 delegates, while Arizona awards its delegates proportionally on the Democratic side.

As voters flooded to the polls, the presidential candidates lashed out at each other’s foreign policy prescriptions, showcasing sharp contrasts in confronting the threat of Islamic extremism.

Clinton – and Trump’s Republican rivals – questioned the Republican front-runner’s temperament and readiness to serve as commander in chief, and condemned his calls to diminish U.S. involvement with NATO.

Addressing cheering supporters in Seattle, Clinton said the attacks in Brussels were a pointed reminder of “how high the stakes are” in 2016.

Cruz seized on Trump’s foreign policy inexperience while declaring that the U.S. is at war with the Islamic State group.

The ultraconservative Texas senator also issued a statement following the Brussels attacks that it was time for law enforcement to “patrol and secure Muslim neighborhoods before they become radicalized,” without providing more details.

Trump’s brash tone has turned off some Republican voters in predominantly Mormon Utah, where early returns suggest Cruz has a chance to claim more than 50 percent of the caucus vote – and with it, all 40 of Utah’s delegates. Trump could earn some delegates should Cruz fail to exceed 50 percent, in which case the delegates would be awarded based on each candidate’s vote total.

Arizona’s win gives Trump a little less than half the delegates allocated so far. That’s still short of the majority needed to clinch the nomination before the party’s national convention this summer.

However, Trump has a path to the nomination if he continues to win states that award all or most of their delegates to the winner. Overall, Trump has accumulated 739 delegates, Cruz has 425 and Kasich 143. It takes 1,237 delegates to win the nomination.

On the Democratic side, Clinton’s delegate advantage is even greater than Trump’s.

The former secretary of state is coming off last week’s five-state sweep of Sanders, who remains popular among his party’s most liberal and younger voters but needs to improve his performance if he expects to stay relevant.

The Vermont senator, now trailing Clinton by more than 300 pledged delegates, had targeted Tuesday’s races as the start of a comeback tour.

He, too, addressed the world’s security threat: “We will stand as a nation with our allies and our friends and people all over this world,” he told supporters in San Diego. “We will stand with them and we will together crush and destroy ISIS.”

For the evening, Clinton stands to win at least 45 delegates to at least 34 for Sanders based on the results in Arizona and Utah.

To date, Clinton has a delegate lead of 1,208 to Sanders’ 878, based on primaries and caucuses. Clinton has at least 1,675 delegates to at least 904 for Sanders when including superdelegates – elected lawmakers and party officials who can cast votes at the convention for any candidate.