Around the world, progressive parties have come to see tight immigration restrictions as unnecessary, even cruel. What if they’re actually the only way for progressivism to flourish?

That the era of low immigration was also the era of progressive triumph is no coincidence. […] The United States felt more like a cohesive nation to many voters, with higher levels of social trust and national pride, and politicians were able to enact higher taxes on the rich and new benefits like Social Security, Medicare and Medicaid.