(CNN) Three Democratic presidential candidates will gather in Des Moines, Iowa, on Saturday night for a debate that has been jolted by the terrorist attacks across Paris that killed more than 100 people and that the French President has declared an "act of war."
The gunfire and explosions in Paris will likely move national security issues to center stage in a Democratic primary that has so far largely focused on progressive issues such as income inequality and controversies like Hillary Clinton's use of private email during her tenure as secretary of state.
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Clinton's views on foreign policy, honed during her time as the Obama administration's top diplomat, could play a large role in the debate, which will start at 9 pm ET. The relative inexperience of her rivals -- Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O'Malley -- on the world stage could also be on display.
CBS, which is hosting Saturday's debate, informed the Democratic candidates that the format would be changed to incorporate questions about the Paris attacks at the the start, a shift met with some resistance from the Sanders campaign.
According to a source on a call between debate organizers and the campaigns, a Sanders aide "completely lost it" when informed of the change and argued that it shouldn't be allowed. After the rift was reported by Yahoo News, Sanders campaign manager Jeff Weaver denied the dispute was resistance to discussing the attacks themselves, saying the conflict revolved around a push to shorten opening statements in order to accommodate for time to talk about the attacks.
"They wanted to make some last minute changes to the debate, we obviously wanted to keep the format to what had been agreed to, and I think people on our staff argued vigorously to that and were successful," Weaver said.
2016 hopefuls express shock, condolences for Paris attacks
The horrific events of Friday, for which ISIS has claimed responsibility, have quickly penetrated the American political world. White House candidates from both parties have reacted to the Paris attacks, offering a mix of condolences and national security policy prescriptions.
Clinton said in a statement Friday that America must stand with its allies and "wage and win the struggle against terrorism and violent extremism."
Sanders said he was "horrified by the cowardly attacks against innocent civilians in Paris."
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O'Malley, meanwhile, offered his prayers and solidarity with the president.
A lot has changed since Clinton, Sanders and O'Malley met for their first showdown in Las Vegas last month.
There were five candidates on stage at the time. Since then, two have dropped out.
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Last month, the possibility of Joe Biden jumping into the race and upending the party's nomination process loomed large -- now, the country knows that the vice president will not pursue another White House bid.
And Clinton, the party's frontrunner, has had plenty of fresh momentum heading into the debate.
After a strong first debate performance, her poll numbers have ticked up and she's widened her lead over Sanders. She now also has the Benghazi hearing behind her -- a day-long affair on Capitol Hill where she largely managed to avoid fresh, negative headlines.
Complete coverage of Paris attacks