The Democratic primary has unleashed a new wellspring of hope on the left for sweeping policy changes. The candidates have been knocking themselves out to propose everything from paid family leave to universal public college tuition—and to one-up each other. Progressives, who’ve watched the party hew to the center too many times, have reason to cheer. But the political reality is more sobering: Most of the far-reaching agenda that Hillary Clinton, Bernie Sanders, and Martin O’Malley have embraced has a slim chance of happening in the next president’s first term, given that Republicans are still likely to control Congress after the 2016 election. (The path to retaking the Senate is extremely narrow, and the path to the House is even more so, thanks to Republican gerrymandering.)

A Democrat who takes over the White House in 2017 is likely to be stuck on the defensive, fending off Republican challenges to President Obama’s accomplishments. That’s not nothing: The Republicans’ promises to dismantle existing legislation and critical regulations—and the high probability that there will be a vacancy on an aging Supreme Court—will ultimately be at the heart of the Democratic case for the White House. 

But while a new Democratic president would face serious constraints, there will be leeway to advance new policy priorities through executive action. While Obama has been far more aggressive in taking unilateral action since Republicans won control of Congress in 2010, he hasn’t exhausted the possibilities—as Clinton, Sanders, and O’Malley are well aware. Since their first debate, the candidates have focused more heavily on issues where there’s significant latitude for the executive branch to act without having to rely on Congress—particularly immigration and criminal-justice reform. When the contenders take the debate stage again on Saturday, Democratic voters should pay particular attention to their exchanges on those issues—and keep their ears tuned to what the candidates say, more broadly, about how aggressive they’d be in taking executive action.

Some liberal pundits are already making the case that Clinton is the best suited to the role of a president who has to find creative ways to get around Congress through executive action. “Clinton is clearly more comfortable than the average person with violating norms and operating in legal gray areas,” writes Vox’s Matt Yglesias. “More than almost anyone else around, she knows where the levers of power lie, and she is comfortable pulling them, procedural niceties be damned.” Since the last debate, Sanders has worked to counter that argument by calling for executive action on immigration. “To the degree that Congress is unable to act, it is clear to me that the president of the United States has got to use the powers that are in his province,” the Vermont senator said at a Las Vegas forum on Monday, vowing to shield far more immigrants from deportation within his first 100 days in office.

Immigration policy offers ample opportunities for executive action—and there’s heavy pressure from the left to act. From the very beginning of her campaign, Clinton vowed to go farther than Obama to shield undocumented immigrants from deportation. Sanders, who voted against the 2007 immigration bill, has been trying to shore up his own bona fides on the issue. And Martin O’Malley, who’s struggling to rise out of the low single digits in the polls, has tried to gain traction by releasing the most detailed and progressive immigration reform agenda in the field so far, including a long list of actions by the executive branch.

The next president could shape deportation policy in far-reaching ways. The chief executive can use his or her prosecutorial discretion to prioritize certain undocumented immigrants for deportation—and make other classes of immigrants far less of a priority. Obama has significantly rolled back deportations over the course of his presidency: During his first term, while hope of getting Republicans on board with a comprehensive overhaul was still alive, he deported immigrants at a record rate; the deportation rate has dropped sharply in Obama’s second term, but it could still go down farther. On Monday, Sanders promised to shield immigrants who’ve been in the U.S. for at least five years from deportation. Clinton has been more vague, but has broadly promised to place new limits on deportation. “I think we have to go back to being a much less harsh and aggressive enforcer,” she said in early October. 

Immigration-reform activists like the sound of that. “For us, the top priority would be delinking immigration law enforcement from criminal law enforcement,” says Chris Newman, legal director of the National Day Labor Organizing Network. “We’ve created this new normal where we think of police stations as venues for deportation.” Even when the Obama administration promised to focus on deporting “criminal aliens,” tens of thousands without criminal records got deported anyway through arrangements with local law-enforcement officials. O’Malley has outlined the most detailed plan to limit cops’ ability to detain undocumented immigrants because of their status. He’s also proposed waivers to allow far more undocumented immigrants to return to their home countries then re-enter the U.S. legally. 

But the path forward on immigration reform becomes murkier when it comes to the future of Obama’s deferred-action program, which he launched in 2012 to shield young undocumented immigrants—or DREAMers—from deportation if they came to the U.S. as children. Both Sanders and Clinton have promised to extend Obama’s deferred action program to the undocumented parents of DREAMers. But it isn’t clear whether an expansion will be feasible—or even whether Obama’s own actions will stand. This week, a federal court ruled that the administration couldn’t implement its 2014 executive actions on immigration, which expanded deferred action to undocumented immigrants over the age of 30 who came to U.S. as children and also shielded the undocumented parents of U.S. citizens and permanent residents from deportation. (Obama has appealed to the Supreme Court.) 

What’s more, the White House originally wanted to extend it to the parents of DREAMers in its 2014 executive action, but concluded that it couldn’t find the legal rationale to do so. A new administration’s lawyers might try to push the envelope, but that would mean a lot more court battles—with an uncertain outcome.  

Since the last Democratic debate, the candidates’ differences on drug policy have also come into sharper relief—and that’s another issue where executive action could make a big difference. Last month, shortly after the debate, Sanders said he’d be open to the legalization of marijuana; he subsequently introduced a bill to remove marijuana from the list of federally prohibited drugs. Clinton has taken a more moderate stance, proposing to reclassify marijuana from a Schedule 1 to a Schedule 2 drug, which would still make it illegal for broad consumption but would make its medical use easier. 

As with immigration reform, the broadest and most effective way to change drug policy would be through congressional action. But there is a pathway for executive action that marijuana-reform advocates are already calling for. “It’s my hope that the next president will lean on her or his agency heads to remove marijuana from the list of federally controlled substances via executive action in order and allow the states to set their own course when it comes to marijuana policy,” says Robert Capecchi, director of federal policies for the Marijuana Policy Project. 

That won’t be simple: The attorney general, Drug Enforcement Agency, and U.S. Food and Drug Administration would all have to be on board with rescheduling the drug, based on medical, scientific, and other policy considerations. A new president could appoint officials who’d be sympathetic to the cause, however, and the active debate that’s already happening on the issue has given new hope to the cause. 

But a new Democratic president might have other reasons to hold back—not just on drug policy, but on executive action altogether. Obama only resorted to aggressive executive action after spending his first term years trying—and failing—to compromise with recalcitrant Republicans. While that political stalemate isn’t likely to ease under a Democratic successor to Obama, a new White House could prompt calls for bipartisanship once more on issues where that hope remains alive. Though hopes have dimmed for Congress’s ability to do even the bare minimum, much less enact bold new policy reforms, there is new bipartisan interest in criminal justice reform. And even if Republicans have swung far to the right on immigration in the primary, that could change in the general election.  

If there’s a glimmer of hope for legislative movement on either front, it could hold back a new Democratic president from acting unilaterally. “It’s much easier to make the case for executive action, and for bold executive action, when Congress has failed to act. It’s much more difficult to act when the Congress is interested in a topic,” says Neera Tanden, president of the Center for American Progress, former Obama administration official, and 2008 Clinton campaign veteran. 

Immigration advocates like Newman, however, warn against a wait-and-see policy, arguing that Obama’s approach to bringing Republicans to the table resulted in real harm to immigrants and their families. He’s encouraged by the Democrats’ current debate over immigration. as it’s actually putting daylight between the candidates and Obama’s executive actions. “Hopefully the candidates will compete to be more progressive and more bold—hopefully, there will be a race to the top,” he says. 

Some on the left would disagree, fearing that going too big on executive action could come back to haunt Democrats over the long haul. As University of Chicago law professor Eric Posner has argued in the New Republic, Obama’s turn to executive action on immigration could end up empowering future Republican presidents to push for non-enforcement of many other laws and regulations—and there are plenty, including environmental regulations and labor protections, that Republicans would love to get their hands on.  

Posner may be right, but shying away from aggressive executive action could doom the next Democratic president to getting little accomplished. The reality is that political gridlock and Republican recalcitrance aren’t going to go away any time soon, and the pressure for the next Democratic president to find new ways to go it alone will only grow. Saturday’s debate will be the next chance for the candidates to show who’s truly best suited to that task.