William Galston is encouraged that the “moderate” Democratic presidential candidate Pete Buttigieg surged to the top of polls in Iowa, and former “moderate” President Barack Obama urged candidates not to veer too far to the left (“Buttigieg and Obama Shake Iowa Up,” Politics & Ideas, Nov. 20).

One doesn’t get the sense that President Obama or Mayor Pete are adamantly opposed to revolutionary change, but the packaging of that agenda in a presidential race has to seem less radical. Democrats can push the envelope and be bold...