Cities are the right frame for tackling many of our most important problems, from concentrated poverty to housing affordability, from economic opportunity to more sustainable living. But enamored as we are of cities, we harbor no illusions that cities, by themselves, can solve our most pressing problems.

Indeed, in the past year, a growing chorus of voices, disillusioned by growing polarization, has called for cities to be our saviors. With control of the national government in the hands of a president of debatable competence and a Republican party seemingly intent on dismantling the federal government, it’s not surprising that many people are looking for reassuring alternatives. Hoping cities can save the day is in many respects an effort to make a virtue of necessity. Bruce Katz and Jeremy Nowak’s recent book The New Localism (2018) relates a litany of instances of Mayors and other civic leaders working above or across partisan and sectoral divides to tackle important problems their cities face. Their approaches are refreshingly innovative, direct and often productive.

There’s an understandable impulse in the face of growing national divisions and what for many was the shocking and unpleasant outcome of the 2016 national elections to retreat to a comforting cocoon of the like-minded. Blue cities will do all the things that solidly Republican national or state governments won’t do: respect LGBTQ rights, provide sanctuary for immigrants, denounce climate change, and tax themselves to pay for needed investments and public services. But withdrawing to the safety of agreeable blue localities cedes the important national battle at just the time when it needs to be contested.

Katz and Nowak marshal an impressive list of inspiring local innovations from cities, such as Indianapolis, Chattanooga, Oklahoma City and St. Louis. Mayors and civic leaders in these places are generally pragmatic and entrepreneurial and are developing solutions that cut across partisan and ideological lines. Cities are, as the saying goes, the laboratories of democracy. But for the most part, they are the small-scale, bench-test laboratories for incubating ideas and showing that they can work at a municipal scale. Implementing these ideas at a national scale is essential to their success.

It is well and good to celebrate the successes that mayors and local leaders are having. But transforming these heartening but small successes into a sweeping call for a new localism is misplaced when the fundamental functions of the national government are being steadily undermined. None of this works in a world in which the federal government is not simply rending holes in the safety net but knocking down its foundations.

Cities are not merely ill-equipped to tackle our major challenges on their own: localism has an undeniable history of making many problems worse. Take two big issues of our time: climate change and surging inequality. Mayors and cities can strike a pose and demonstrate effective tactics, but they lack the policy throw-weight to solve these problems. However, it’s almost impossible to imagine that we’ll take effective action to address climate change unless it’s done at a national level in cooperation with the rest of the world. Without a federally imposed carbon tax or cap and trade, localized efforts are likely simply to relocate the dirtiest pollution to the most permissive states.

Indeed, many of the innovative city strategies celebrated in The New Localism are directly dependent on the ability of mayors and city institutions to tap into federal largesse. Take Pittsburgh, heralded as an exemplar of local innovation. Katz and Nowak acknowledge that Carnegie Mellon and the University of Pittsburgh receive more than $1 billion in federal research funding annually. Cities looking to exploit an “eds and meds” strategy can’t do it without huge federal support in the form of research grants, student aid, Medicare, Medicaid and the Affordable Care Act. A federal government that defunds these programs—as seems likely because of the new tax reform law—will make it all but impossible for cities to innovate.

The key lesson of policy experimentation is that while ideas can be tested and refined at the state or local level, they ultimately need to be national in scope. States experimented with minimum wage laws, unemployment insurance, and old age pensions, but none of these were began to address our problems until extended nationwide in the New Deal.

The danger is that calls for renewed localism effectively aid and abet the ongoing efforts to systematically dismantle federal programs. The clarion call to act locally diverts our political attention from the national stage and perhaps, unwittingly, becomes an excuse to stand by and watch these foundational programs be destroyed.

For a long time, we could take the federal government more or less for granted. There was no hope that it would ride to the rescue, but at least it would keep doing what it had always done: cashing social security checks, bankrolling medical care for the poor and aged, enforcing a minimum of civil rights everywhere, engaging seriously with the rest of the world on global issues. Now, every one of those fundamental roles is very much in jeopardy. If the poor lose health care, are turned out of subsidized housing, see their education prospects dim, that will directly add to the costs burdening states and cities. The pressure to fill in for a diminished federal presence will greatly handicap local innovation.

If you care about cities and believe local initiative can lead to solutions, you need to be marching on Washington and fighting for a federal government that does its job well. The hollowing out of the federal government now underway is the clearest threat to creative, effective localism. Ultimately, the magic of our federal system is that both national and local government have important and complementary roles to play. It’s not either/or. It is both/and. Innovative cities require a supportive federal government.

Read the complete essay by Joe Cortright, Qualms about the new localism: Cities need the national government to do its job well, on City Observatory’s website.