This week, the Center for American Progress, the most prominent Democratic think tank in Washington, is holding an “Ideas Conference” at a moment when the Trump administration seems to be melting down. If you’re thinking of running for president in 2020, you were on the speakers’ list — Elizabeth Warren, Kirsten Gillibrand, Cory Booker, Amy Klobuchar and many others were scheduled to speak. Along with the conference, CAP released a report called “Toward a Marshall Plan for America.”

These kinds of think tank reports seldom make for the most exciting reading, but they’re important because they end up being translated into policies that affect all of our lives. When the next Democratic president takes office, he or she will arrive with a set of plans that have been worked out at places like CAP in the time since the last election.

There’s also a vital political question the report is meant to answer: Can Democrats articulate an economic vision that voters find compelling in 2018 and 2020?

That’s a question that goes beyond the details of policy. Democrats find it somewhere between maddening and incomprehensible that they don’t win on this issue every time. They see polls showing that the policies they support (a higher minimum wage, paid family and sick leave, infrastructure investments and so on) are enormously popular, while the centerpiece of all Republican economic policy (tax cuts for the wealthy) is hugely unpopular, and they tear their hair out. How can voters ever believe Republicans will do better on the economy than they will? Why do so many routinely tell pollsters that they trust Republicans more on the economy?

In light of recent history, these questions are particularly infuriating for Democrats. The economy performed extremely well under Bill Clinton, then George W. Bush came into office and it performed terribly, then Barack Obama came into office and pulled the country out of the Great Recession, and then Donald Trump came along with a plan to do almost exactly what Bush did, and somehow enough voters said, “That sounds like a good idea.”

The conclusion many Democrats are coming to is that while their problem isn’t entirely one of packaging, packaging is an important part of the answer. They have to put their laundry list of ideas together into a coherent synthesis that they can present to the public and easily explain why they think it will work. If you can’t get the voters to buy what you’re selling, you’ll never get the chance to prove its merit.

Polling suggests a large proportion of those who had voted for Barack Obama but then voted for Trump believed that Democrats’ economic policies would favor the wealthy, while Trump’s wouldn’t. The reflexive — and quite reasonable — response Democrats have to findings like that is to cry out in anguish and curse those voters for their ignorance. It’s like saying you voted for a Republican because you thought he’d be more likely to protect abortion rights, or you voted for a Democrat because you thought they’d be more likely to cut domestic spending. It isn’t a matter of opinion; it’s just wrong.

Democrats have to solve that political problem — but that doesn’t mean doing so won’t help them detail and refine a program that can be put into place the next time they have the opportunity. The political and substantive questions are tied together. As the CAP report argues, “The economy is not producing access to a good, stable middle-class life for people who do not go to college, and those voters are likely to continue to disrupt the political system until it does.”

You can hope people’s displeasure at those conditions might eventually be turned on Republicans, and by 2020 it might, particularly since voters usually assign blame and credit for the state of the economy to the president’s party, whether the party deserves it. But it will be awfully helpful for Democrats if they can point to a program they have ready to go that will specifically address the concerns of those who are struggling.

While CAP says it’s forming a commission to work through the details of this Marshall Plan, the centerpiece is “a large-scale, permanent program of public employment and infrastructure investment — similar to the Works Progress Administration during the Great Depression but modernized for the 21st century.” It assumes that such a program would employ 4.4 million people at $15 per hour, costing “about $158 billion in the current year. This is approximately one-quarter of Trump’s proposed tax cut for the wealthy on an annual basis.” That would essentially make the government the employer of last resort — if you can’t find a job, you can get one working on infrastructure projects or other tasks that help build up your community.

We can have a detailed debate about the pluses and minuses of that kind of approach, but that’s a debate Democrats should welcome. It’s not that it isn’t politically effective enough to just say “Republicans are the party of the rich” — it often is politically effective enough, not least because it’s true. But it’ll be a lot better for Democrats if they have a clear and explainable version of the other side of their argument.

One thing we don’t yet know is how much Trump will help them in making that argument. While he has certainly been as aggressive as any Republican in advancing the interests of the wealthy and powerful, the truth is that most voters don’t know what’s in his tax-cut plan or how many Goldman Sachs alums he has making economic policy. If the economy where they live does better than it’s doing now, they’ll give him credit for it. But if it doesn’t, Democrats will have the chance to make their case. They’d better be ready.

Paul Waldman is a contributor to The Washington Post’s Plum Line blog, and he is also a senior writer at The American Prospect.