Sen. Bernie Sanders (I-Vt.). (John Minchillo/Associated Press)

DEMOCRATS ARE licking their wounds, arguing about what or whom to blame and opening a fight over who should next lead the party. That’s normal after losing the presidency, both chambers of Congress and all but 15 governorships. They also are beginning to argue about what the party should stand for. That, too, is normal — and potentially healthy. The country will be better off if it has a vibrant, left-of-center party making the case for progressive views.

But what does it mean to be progressive? We don’t propose to lay out an agenda here — this is a debate that will and should go on for months, hopefully drawing on new ideas and up-and-coming leaders, and we expect to return to it often. We would, though, like to suggest that in some key areas, the people who are defining themselves as the progressive wing of the Democratic Party — identified with Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) — are embracing principles that are not genuinely progressive.

Specifically: They want to enlarge government entitlements and hand out the benefits as broadly as possible — free college, free health care, expanded Social Security — regardless of need or available resources. They emphasize redistribution over growth. And their ostensible protection of American workers leaves no room to consider the welfare of poor people elsewhere in the world. On all three counts, we think that the higher moral ground and the smarter policy lie elsewhere.

Take free college, a key plank of Mr. Sanders’s presidential campaign. Generally two arguments are offered for making such a benefit universal. One is political: If everyone gets a benefit, everyone will press Congress or state legislatures to keep funding it. The other is moral: This is something society should do. We don’t make the wealthy pay tuition for high school; why should college be any different?

Our answer — we would argue, the progressive answer — is that there are people in society with far greater needs than that upper-middle-class family in Fairfax County that would be relieved of its tuition burden at the College of William & Mary if Mr. Sanders got his wish. In an era of constrained resources, is the nation serious about helping the “left-behinds” in small-town America, whose plight President-elect Donald Trump supposedly championed? How about the mothers and children who remain trapped in multi-generational poverty in our biggest cities? Government programs should benefit those who most need the hand up.

The same is true of Social Security. You can expand benefits for everyone, as Ms. Warren favors. Prosperous retirees who live mostly off their well-padded 401(k)s will appreciate what to them will feel like a small bonus, if they notice it. But spreading wealth that way will make it harder to find the resources for the vulnerable elderly who truly depend on Social Security.

Here we pause for a moment of preventive self-defense, because the fiscal argument is easy to caricature. When we say that resources are constrained, we are not arguing that the budget has to be balanced tomorrow. We are not arguing against investments in infrastructure, education and research — all of which we favor.

But demographics — the aging of the population — cannot be wished away. In the 1960s, about five taxpayers were helping to support each Social Security recipient, and the economy was growing about 6 percent annually. Today there are fewer than three workers for each pensioner, and the growth rate even following the 2008 recession has averaged about 2 percent . On current trends, 10 years from now the federal government will be spending almost all its money on Medicare, Social Security and other entitlements and on interest payments on the debt, leaving less and less for schools, housing and job training. There is nothing progressive about that.

That is one reason we say that economic growth is also a progressive goal. It’s not a sufficient goal; growth must be shared, not vacuumed up by the top 1 percent. It’s not in conflict with the goal of redistribution; there’s reason to think that inequality can retard growth. But over the course of U.S. history, economic growth has been key to the rising prosperity of all Americans.

What does that mean for policy? Can government spur growth, and if so, how? That is a fraught debate. At a minimum, though, a progressive should favor growth, think twice before vilifying business as a whole and consider the effect on jobs when advocating additional regulations.

Finally, when true progressives think about trade and the world, they ought to keep in mind a statistic that President Obama cited in his final address to the U.N. General Assembly: The share of people living in extreme poverty in the world fell over the past quarter-century from 40 percent to under 10 percent. That’s an astounding achievement for human progress, unique in world history, taking place even as global population grew — and mostly thanks to the globalization of the economy. That trend is good for Americans, economically, because it gives them markets to sell into. But the decrease in human misery also should be celebrated for its own sake.

We understand the political challenges underlying these arguments. Mr. Trump campaigned on proposals that would grow the federal debt far more than any Democrat’s program, and his benefits would be targeted — to the wealthy. His proposals on trade would be far more destructive. In opposing every government program and regulation as a job-killer — including, wrongly, Obamacare — the Republicans make a rational discussion of trade-offs almost impossible.

If they attempt to govern on the basis of these proposals, why should Democrats, in the minority, be any more responsible? Far easier to claim to be standing up for the American worker by bashing China or Mexico, declaring that every problem can be solved by soaking the rich and promising government benefits to every voting family.

But if Democrats hope to deserve electoral gains in 2018 and beyond, they will need to do more than oppose Mr. Trump while outdoing him in undeliverable promises. They will need a constructive, 21st-century version of progressivism — one that embraces growth, fairness and opportunity for everyone.