Things clump together; the periphery cannot hold.

As you read this, Democratic presidential hopefuls are crisscrossing Iowa, trying to assure farmers that they share their concerns. Commentators are publishing opinion pieces about how Democrats can win back rural voters. Think tanks are issuing manifestoes about reviving heartland economies.

There’s nothing wrong with discussing these issues. Rural lives matter — we’re all Americans, and deserve to share in the nation’s wealth. Rural votes matter even more; like it or not, our political system gives hugely disproportionate weight to less populous states, which are also generally states with relatively rural populations.

But it’s also important to get real. There are powerful forces behind the relative and in some cases absolute economic decline of rural America — and the truth is that nobody knows how to reverse those forces.

Put it this way: Many of the problems facing America have easy technical solutions; all we lack is the political will. Every other advanced country provides universal health care. Affordable child care is within easy reach. Rebuilding our fraying infrastructure would be expensive, but we can afford it — and it might well pay for itself.