DES MOINES, Iowa – Coming just about 24 hours after the devastating terror attacks in Paris, the second Democratic presidential debate here Saturday night will take on a somber tone and a very different set of issues than originally planned, complicating the night for challengers Bernie Sanders and Martin O’Malley.

Security will be tight, and CBS News, which is broadcasting the debate, said it will start with a discussion of the attacks, which are believed to have been the work of the Islamic State of Iraq and Syria (ISIS), but will include other topics as well.

“It caused us to refocus some of the questions on what happened in Paris and the threat of terrorism and how the candidates would respond to that threat if they were president,” said Christopher Isham, the Washington bureau chief of CBS News. ”We will continue to ask about other topics. This is not going to become a foreign policy debate.”

Sanders and O’Malley have both been telegraphing much sharper attacks against frontrunner Hillary Clinton in an effort to blunt her momentum, and feel they can forge ahead with their original plan, despite a potential risk of looking overly political during a time of mourning.

Still, even her rivals say the new issue terrain favors Clinton, the former secretary of state who has advocated a more muscular foreign policy. ”I think everybody realizes that Hillary Clinton’s experience as secretary of state gives her a lot of standing,” Sanders senior strategist Tad Devine acknowledged to MSNBC, conceding she has “a huge advantage” on these issues.

Democrat strategist Chris Kofinis conducted a focus group Friday night in Iowa with 31 Democratic voters and found that Clinton ”is nearly unanimously viewed as a stronger commander-in-chief.” He added that “Sanders was extremely vulnerable on this issue before Paris, and this is even truer now.”

Still, Devine said of the new focus on terrorism, “I don’t think it changes the strategy at all,” adding, “One thing you don’t want to do is move away from a message if you believe you’ve got the wining message.”

O’Malley and Sanders are both likely to stay on course with plans to point out sharp differences with Clinton. O’Malley sees a chance to demonstrate leadership and surprise observers who hold rock-bottom expectations. Sanders, meanwhile, sees an opportunity to share with voters his views on an issue he rarely discusses. Other important issues should not be ignored or put on hold, they say, and the CBS moderates seem inclined to agree.

The debate was already going to be a quieter affair than the first face-off last month amid the bright lights of the Las Vegas strip. In addition to a simpler setting on the campus of Drake University, the event was scheduled for 9 p.m. ET on a Saturday, when fewer people are likely to watch. Meanwhile, the field has winnowed and Clinton, the front-runner, has re-solidified her lead.

Nonetheless, the debate will carry outsize importance here in Iowa, the state that holds the first presidential nominating contest and is critical to all three of the candidates’ strategy to win the nomination.

National Security and terrorism

On Friday, terrorism went from almost a non-issue in the Democratic primary to the most important one, at least for Saturday’s debate. According to the latest NBC News/Wall Street Journal poll, just 2% of Democratic primary voters said that terrorism was their top concern, while another 4% picked foreign policy and the Middle East.

Instead, the primary has focused on issues like economic inequality, racial justice and college affordability. Sanders has long been a critic of U.S. foreign policy, but he has little direct experience on the issue and does not serve on any Senate committees that deal with defense or foreign policy. Just last week, he voted against a defense authorization bill, saying it spent too much money and did not crack down on fraud.

Governors like O’Malley are generally considered to have a disadvantage on foreign policy, since they don’t have to deal with it. Clinton, meanwhile, has been the nation’s top diplomat, and has served on the Senate Armed Services Committee.



Low bar for Clinton

The stakes for Clinton were already dramatically different from the first debate. Then, Clinton was coming off a brutal month and was untested in the crucible of a recent presidential debate. But she turned in a commanding performance, in which she showed that she can land a punch on her fellow Democrats, and was almost universally considered the winner. Now, with her polls back up and her lead more secure than ever, a steady, mistake-free outing will do just fine.

Awkward offense

For Sanders and O’Malley, the picture could not be more different. Recent polls suggest Sanders’ momentum may have stalled, while O’Malley’s campaign is running out of money and is still stuck in the single digits in most polls.

To change this, both candidates have been drawing ever sharper contrasts with Clinton, and, until Friday night, looked ready to swing harder and more frequently in the second debate. But now, in a moment of tragedy, attacking Clinton too harshly could backfire.

Immigration

Immigration has been a minor issue in the Democratic primary so far, but it was lining up to be at the forefront of Saturday’s debate. O’Malley and Sanders attended a Latino event in Las Vegas this week where the former attacked his two rivals and Sanders rolled out an immigration plan.

Local issues

The debate in Las Vegas attracted more national attention than Saturday’s in Iowa is likely to. So campaigns for each of the candidates suggest there will be a greater focus on local Iowa issues, such as knocks on Republican Gov. Terry Branstad.

The debate about debates

The Democratic debate schedule has been extremely controversial, but this is the first time it’s really been put to the test with a weekend debate. Saturday debates are highly unusual, since fewer people watch TV on weekends.

Supporters of Sanders and O’Malley accused Democratic National Committee Chair Debbie Wasserman Schultz of shunting the debates to weekends to limit the potential impact on Clinton, whose 2008 presidential campaign Wasserman Schultz helped lead.

This story has been updated.