This is not an accurate characterization of the left-right divide in U.S. politics since there is actually little difference between Republicans and Democrats or self-described conservatives and liberals in their support of the key components of the social safety net: Social Security, Medicare, Medicaid, and even unemployment insurance. Polls consistently show that the overwhelming majority of people across the political spectrum strongly support keeping these programs at their current level or even expanding them.
Public polls do demonstrate that the American public supports (with incredible majorities) Social Security, Medicaid, and Medicare. Only 22% of the public thinks we should cut spending on health care programs; that number shrinks to 15% for Medicare specifically, and 10% for Social Security.
However, Krugman’s main point was that the left-right debate over the size of the social-welfare state boils down to an argument over the size of the federal tax burden. The CEPR response doesn’t really address that; for starters, there is no federal program for which a majority of the country supports cutting spending–and, as the polls show above, very very small proportions of the country support cutting spending to the major programs in the social-safety net. However, when asked about general spending (and not specific programs), a majority of the country supports cutting spending.
I think what this really boils down to is the lack of precision in public polling (or, rather, the dearth of a well-informed citizenry). People like the specific programs that government provides. However, the American public is very philosophically opposed to federal government spending. So, majorities of democrats and republicans support maintaining Medicare/Social Security and majorities of democrats and republicans support cutting federal spending across the board. However, (and this goes back to Krugman’s point, I think), clearly our federal tax burden will have to rise if we want to maintain our current spending levels on Medicare, Social Security, and Medicaid moving forward. I’d be curious to see what sort of support a poll asking if “the America public would be willing to raise taxes to support current levels of Medicare and Social Security spending” would generate. My guess is that polling on a question asking about a tradeoff between tax rates and medicare spending would divide support a lot more evenly along a (self-described) left-right axis.