Over the decades, conservatives have been enormously successful at selling a parody of liberalism. Liberals are cast as dreamy idealists who think “throwing money at problems” is the way to solve them. They’re painted as hostile to a tough-minded examination of their programs and indifferent to whether they work.

This parody has things exactly backward. In 2021, it’s liberals who want citizens, politicians included, to look rigorously at the evidence. It shows how many public programs make a substantial, positive difference in the lives of Americans, especially kids from low-income families. It’s conservatives who prefer ideology and moralism to the facts.

The spending that liberals favor these days — much of it included in President Biden’s American Families Plan that Democrats are pushing through Congress — is for government interventions that have been tested and proved.

The phrase “laboratories of democracy” refers to how state governments are free to try different policy approaches, giving all of us a chance to see which are successful and which aren’t.

The idea is often misused by opponents of federal action to argue that we should leave as much as possible to the states. Thinking of the states as “laboratories” points in a different direction. If states — red and blue — show that certain policies plainly improve people’s opportunities and circumstances, doesn’t it make sense to apply them to the whole country? Key programs, starting with Social Security and Medicare, are national for a reason.

This underscores the importance of a report released this month by the Center on Budget and Policy Priorities (CBPP), a think tank devoted to careful policy analysis aimed at lifting up those who have been left out. Citing study after study, the report concludes that “a large body of research” demonstrates the policies in Biden’s package and other forms of assistance to the needy “would make a substantial difference in the lives of children and youth.”

Just a few particulars from the report written by Arloc Sherman, Ali Safawi, Zoë Neuberger and Will Fischer:

“When children grew up in a household receiving additional cash benefits, their academic achievement increased on a lasting basis.”

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“When elementary and middle school students received access to free school lunches, their academic performance improved.”

“When children had access to quality pre-kindergarten at age 4, they were likelier to enter college on time.”

“When high school students were guaranteed grants to pay for community college, they were likelier to complete community college.”

“When parents had access to paid family leave, rates of early births and low birthweights declined.”

There’s much more about what works. Footnoting proves nothing by itself, but this document’s 108 footnotes are a measure of how many high-quality, nonpartisan studies have tested the effect of various policies.

Sharon Parrott, president of the CBPP, said in an interview that the research pulled together underscores that programs Biden and other progressives are proposing are bold but not radical. (It’s one reason the polls show them to be popular.)

“Many of them are building on successful but underfunded programs” nationally and in the states, she said, or programs that work well in other well-off democracies. Without intending an ideological pun, she added that Biden’s proposals are not “out of left field.”

Parrott offered a common-sense point, often overlooked, about why a society that says it cares about “family values” should want to help parents with young children through programs such as the child tax credit.

On the whole, earnings rise as people get older, but they tend to have children when they are younger. “We ask people to spend a lot of money” on child-rearing “at the time when they’re earning the least,” she noted. Smoothing out the imperatives of the life cycle for middle-class and poor families is good for parents and children alike.

There is no rational reason the child poverty rate needs to be as high as it is in the United States. The percentage of children living in poverty in this country based on market incomes is not all that different from the share in most of 18 other rich countries. But an analysis of pre-pandemic data from the Organization for Economic Cooperation and Development — that is, from before the covid-fueled surge of social spending — found that when public policies relating to taxes and benefits were taken into account, the United States ranked dead last.

We should do better. With smart policies, we can.

A major obstacle to more energetic efforts to help the least advantaged, Parrott said, is “the cynicism that it doesn’t matter what we do.” But it does matter. When it comes to public programs, the antithesis of cynicism is reality itself: We know a great deal about what works. Let’s do it.