As the 2020 presidential campaign heats up, debates will play a big role. Already the Democrats have announced the dates and locations for their first two debates. These will help shape a large and raucous field. And the fall 2020 debates between President Trump and whoever the Democrats settle on will help determine if Trump gets another four years of his controversial presidency.

While all eyes are on the candidates and the president, more attention should be paid to the individuals who will moderate the coming debates. They play a crucial role and often stand between a debate that is informative and one that is a waste of voters’ time.

There are three types of debate moderators. The first type is the worst type. That moderator lets a candidate or candidates take over and fails to hold candidates accountable for answering the questions asked. In this case, the moderator plays the role of spectator–and voters get virtually nothing out of it.

The second type of moderator maintains order but is meek, often refusing to challenge candidates or demand that candidates answer questions directly. These moderators often fail to ask difficult questions initially or pointed follow-up questions. While some information gets out in some debates, the moderators ensure that such information is limited. For example, in one of the Republican primary debates, it became clear that Donald Trump did not know what the nuclear triad was. He gave the moderator, Hugh Hewitt, a rambling answer that talked about Iraq and Syria–not American capability to deliver nuclear weapons via bombers, ICBMs or submarines. Hewitt tried to help him along by following up with a question about which of the three legs of the triad Trump thinks is most important. Once again, Trump punted. Hewitt never did ask Trump point-blank for a definition of the triad. Sen. Marco Rubio (R-Fla.) did that in a follow up. Hewitt let Trump off the hook, leaving a handful of print journalists to point out that Trump did not know the first thing about a central concern of an American president.

The last kind of moderator is the master. She controls the pace of and behavior within a debate. She holds candidates accountable for the words in the debate and their words prior to the debate. That moderator will ask pointed, probing follow up questions. This difficult yet skillful approach is not meant to put a candidate in a “gotcha” situation. Instead, the approach demands that candidates communicate with voters and inform them.

We all need a lot more of the latter, and this year (and next), moderators will face an important situation, both in the Democratic field and the general election; they owe it to voters to get it right. Moderators in 2016 did little to push Trump on his claim that he would make Mexico pay for the wall on the southern border. It was as ridiculous then as it is now, but time and again, the bumper sticker message was allowed to stand.

On the Democratic side, many of the 2020 presidential candidates have big, bold, far-reaching policy proposals. Many of these ideas—if enacted—would dramatically transform public policy and society. But they are, in many cases, a big “if.” Most of these bold ideas will not be enacted by Congress in 2021. Control of the Senate, the 60-vote filibuster requirement, and a coalition of Democrats that includes moderates from red and purple states will muddy plans to enact the dream legislation of the Democratic Party’s most staunch progressives. That is not to say discussing bold policies, in either party is a bad idea. Those visionary ideas help inform voters of candidates’ true values and can motivate effective bargaining and motivate other policy change–but acting as if there are no downsides to these proposals and accepting unrealistic plans for paying for them doesn’t serve the voters’ interests.

While some conservatives and progressives eschew pragmatism, the realities of governing—particularly for a president—require it. Debate moderators should allow and encourage candidates to discuss their lofty ideas. Then, moderates should say, “Thank you. Next?” Those moderators need to push candidates to discuss their Plan B. When lofty policy ideas fall short in Congress, moderators must ask candidates whether they would be satisfied with the status quo or try something more pragmatic, or incremental. They should ask candidates which component parts of policy problems do they find most in need of repair and how might those component parts be addressed. Voters should know not simply the ideal policy a candidate supports, but what that candidate could tolerate to advance the cause for change. Too often candidates are not pushed to detail their governing approach and voters are left unaware of what’s next.

And this approach is not something to be reserved for progressive Democrats. General election debates must push President Trump in the same way. In 2016, primary and general election debate moderators were less than effective at holding Mr. Trump to account for his promises on health care, Social Security, Medicare, a Mexican-funded wall along the southern border, etc. First, moderators must demand details of candidate proposals. Second, they must ask candidates the details of their alternative approaches to governing.

Simply discussing policy in a debate does not prepare voters to make decisions. Demanding candidates operate in the political reality of partisanship, polarization, and the structure of our governing institutions is a must. Moderators who operate in this way will advance our democratic understanding in two ways. First, they will serve as models for other moderators, training others how best to fill this important role in our polity and society. Second, such moderator behavior will put this year’s candidates and future candidates on notice. No longer will candidates get by simply by chirping idealism, speaking with vacant platitudes, and rejecting the basic necessities of governing and negotiation. This will push candidates—at least effective ones—to be better. And in the process, they will offer something this country desperately needs: easy-to-access information that assists voters in making one of the most important political decisions of their lives.