Hillary Clinton and Donald Trump exchange barbs after latest round of primaries
Republican Donald Trump and Democrat Hillary Clinton traded wins with their chief rivals on Tuesday and attacked each other's foreign policy views as the 2016 presidential contest turned into a clash over who could best deal with the threat of Islamic extremism.
While both frontrunners scored victories in the night's biggest prize of Arizona, Democratic challenger Bernie Sanders won caucuses in Utah and Idaho and Republican Ted Cruz claimed his party's caucuses in Utah.
The victories kept Mrs Clinton and Mr Trump from dominating another election night, but they both maintained a comfortable lead in the race for delegates who will choose each party's nominee at national conventions in July.
Long queues and high interest marked primary elections across the three Western states 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 metro 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," Mrs Clinton said in Seattle as she condemned Mr 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."
Mr Trump, in turn, branded Mrs 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.
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.
Mrs Clinton - and Mr 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 US involvement with Nato.
Addressing cheering supporters in Seattle, Mrs Clinton said the attacks in Brussels were a pointed reminder of "how high the stakes are" in 2016.
"We don't build walls or turn our back on our allies," she said, in an apparent reference to Mr Trump's call to build a wall along the Mexican border. "We can't throw out everything we know about what works and what doesn't and start torturing people."
Mr Cruz seized on Mr Trump's foreign policy inexperience while declaring that the US is at war with the Islamic State group.
"He doesn't have the minimal knowledge one would expect from a staffer at the State Department, much less from the commander in chief," Mr Cruz told reporters. "The stakes are too high for learning on the job."
The ultraconservative Texas senator also issued a statement following the Brussels attacks that it was time for law enforcement to "patrol and secure Muslim neighbourhoods before they become radicalised", without providing more details.
In interviews on CNN, Mr Trump said he supported Mr Cruz's surveillance proposal "100%", while Ohio governor John Kasich opposed it.
Mr Trump's brash tone has turned off some Republican voters in predominantly Mormon Utah, where Mr Cruz claimed more than half of the caucus vote - and with it, all 40 of Utah's delegates.
Yet that would not make up for Mr Trump's haul in Arizona, where he earned the state's entire trove of 58 delegates.
Arizona's win gives Mr Trump a little less than half of the Republican delegates allocated so far. That is still short of the majority needed to clinch the nomination before the party's national convention this summer.
However, Mr 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, Mr Trump has accumulated 739 delegates, Mr Cruz has 465 and Mr Kasich 143. It takes 1,237 delegates to win the Republican nomination.
Mr Trump's rivals' best hope is to deprive him of the majority of delegates needed to win the nomination outright and force a contested convention.
On the Democratic side, Mrs Clinton's delegate advantage is even greater than Mr Trump's.
Coming off last week's five-state sweep of Mr Sanders, the former secretary of state entered Tuesday leading by more than 300 pledged delegates. With Mr Sanders standing to win at least 57 delegates to Mrs Clinton's 51 on Tuesday, that was not about to change.
Neither was Mr Sanders' commitment to carry on.
"These decisive victories in Idaho and Utah give me confidence that we will continue to win major victories in the coming contests," he said in a statement.
Still, Mrs Clinton now has a total delegate lead of 1,214 to Sanders' 901, based on primary and caucus results. Overall, Mrs Clinton has at least 1,681 delegates to Mr Sanders' 927 when including superdelegates, Democratic lawmakers and party officials who can vote for any candidate at the convention.
Jeb Bush later announced that he is endorsing Mr Cruz for president.
Mr Bush tweeted: "Ted is a consistent, principled conservative who has shown he can unite the party."
He added on his Facebook page that the Republicans "must overcome the divisiveness and vulgarity Donald Trump has brought into the political arena" or risk losing to Mrs Clinton.