When the Democratic presidential contenders gathered on the debate stage in Des Moines, Iowa, on Saturday, just hours after a series of terrorist attacks in Paris left at least 129 people dead, the candidates spent the early portion of their time on stage examining issues related to national security. They spoke of boots on the ground, regime changes, what role the United States ought to play in the fight against ISIS, and whether or not they use the term “radical Islam.”

But curiously, throughout the lengthy discussion, the one issue that was never mentioned—not once—was encryption. That’s lucky, at least for the candidates. As the world continues to reel from the Paris attacks, the debate over whether tech companies like Apple and Google are allowed to fully encrypt users’ communications will, no doubt, become one of the central dramas of the national security conversation going into the 2016 presidential race. It may also be among the toughest issues for the candidates, especially Democrats, to navigate.

Encryption may be among the toughest issues for the candidates, especially Democrats, to navigate.

Just yesterday, CIA director John Brennan said that he hoped the Paris attacks would serve as “a wakeup call” to those who oppose government surveillance in favor of personal privacy.

“There are a lot of technological capabilities that are available right now that make it exceptionally difficult both technically as well as legally for intelligence security services to have insight that they need to uncover it," he said, adding that terrorists have “gone to school” to figure out ways to evade intelligence officials.

Brennan attributed that fact, in part, to Edward Snowden’s disclosures of the National Security Agency’s bulk data collection programs, saying they tipped would-be terrorists off to surveillance tactics. “In the past several years, because of a number of unauthorized disclosures and a lot of hand-wringing over the government’s role in the effort to try to uncover these terrorists,” he said, “there have been some policy and legal and other actions that make our ability, collectively, internationally, to find these terrorists much more challenging.”

This, of course, is not the first time we’ve heard these concerns from government officials. Just a day before the Paris attacks, the NSA’s former general counsel, Matt Olsen, told an audience gathered in Des Moines that after Snowden came forward, the agency “lost track of terrorists.” Meanwhile, FBI director James Comey has been an outspoken critic of encryption, arguing that it enables criminals to “go dark.”

Whether encryption is really the security risk the government makes it out to be, of course, is still up for debate. We at WIRED have debated it plenty. Now it's time for the presidential candidates to do the same.

Democrats' Conundrum

Until now, the Democratic candidates in particular have been light on detail about where they stand on encryption and surveillance. This reticence stands to reason. By aligning themselves too closely with Washington's intelligence community, they could alienate their Silicon Valley base, which is increasingly powerful in politics. But if they cater too much to the interests of tech companies such as Apple and Google, they could lose favor among voters who increasingly see national security as the country's most pressing issue.

Former Secretary of State Hillary Clinton has walked an uneasy line on the subject of surveillance in the past. On one hand, she was a supporter of the controversial PATRIOT Act as a senator back in 2001, a decision that's been widely criticized by Bernie Sanders' camp. This summer, she also said that cybersecurity legislation such as the Cybersecurity Information Sharing Act, or CISA, which is already highly unpopular among privacy advocates, doesn't go far enough in encouraging tech companies to share information with the US government. And during the first debate, she said Snowden "stole very important information that has unfortunately fallen into a lot of the wrong hands," and that he shouldn't return home "without facing the music."

'I think there are really strong, legitimate arguments on both sides.' Hillary Clinton

At the same time, however, she has endorsed the USA Freedom Act, which would end the NSA's bulk data collection program, calling it "a good step forward in ongoing efforts to protect our security and civil liberties." And at a conference earlier this year, Clinton told Re/Code's Kara Swisher that encryption is "a classic hard choice," but she hedged before offering up her plan for what to do about it. "I would be the first to say I don't have the answer," she said. "I think there are really strong, legitimate arguments on both sides."

Vermont Senator Bernie Sanders, on the other hand, has been far more outspoken in his opposition of government surveillance. He received a round of applause at the first Democratic debate for voting against the PATRIOT Act and has said that, as president, he would shut down the NSA's surveillance program altogether.

But national security is considered Sanders' major weak spot. Even those who support his stance on inequality sometimes question his ability as commander-in-chief. The more fearful Americans become of the threat ISIS poses, the weaker Sanders' stance on surveillance may appear to the electorate beyond Sanders' base. After all, a recent poll showed that 56 percent of voters said they would give the government access to some personal data if it meant protecting the country from a terrorist attack.

Keeping Both Sides Happy

On the other side of the aisle, candidates like Jeb Bush, Marco Rubio, Carly Fiorina, Donald Trump, and Chris Christie have all spoken out against encryption and the need for government surveillance. The one notable exception, of course, is Kentucky Sen. Rand Paul, who said at a conference last week that he believes governments should require warrants to access people's communications. Still, that policy doesn't apply to companies like Apple, which promises users that their data is encrypted so that it can't be accessed even with a warrant.

The battle over how to balance security and privacy, of course, is nothing new in politics. Just last month, the Obama administration backed away from legislation that would have forced tech companies to decrypt messages for law enforcement. The move was seen as a win for technologists and privacy advocates alike.

Those same advocates are now hoping that fear won't cause politicians to resume the fight against encryption. "The Paris attacks are absolutely tragic, but the response must not be to undermine cybersecurity for digital services on which many millions of people depend," said Harley Geiger, senior counsel and advocacy director for the Center for Democracy & Technology. "Weakening encryption will also not prevent organized groups from using strong encryption. Difficult-to-crack encryption and apps will continue to be available on the Internet, even if governments seek to ban them."

And yet, as calls for stronger national security spread post-Paris, candidates that support encryption may face added pressures from both the public and their Republican opponents to reevaluate—or at the least, delineate—where they stand on encryption. And when they do, they may find it's not so easy to keep both sides happy.