More than 550,000 people in the United States are homeless on any given night. More than 18 million spend more than half of their income on housing. And there is no state in which the number of affordable homes matches the number of low-income households.

Affordable housing, or the lack thereof, is a crisis no matter which way you slice it, and has been for many years. But it has never gotten as much attention in a presidential campaign as it is getting now, with candidates proposing hundreds of billions of dollars in new spending and terms like redlining and Section 8 starring in stump speeches.

And the public debate over housing and homelessness has grown increasingly prominent in many of the states voting on Super Tuesday, such as California, where the crisis has been particularly acute.

A new survey of the Democratic candidates on a variety of housing policies, conducted last week by The New York Times, finds they are largely united on offering incentives for affordable development and increasing tenant protections. But the responses to the questionnaire also revealed significant differences, including on rent control.