But in light of objective conditions, Obama should be more vulnerable. Health-care reform, his signature presidential achievement, is durably unpopular. Economic growth under Obama has only slightly exceeded the average of the 1930s. Chronic unemployment and housing-market declines are at their worst levels since the Great Depression. The number of people in poverty has increased at a record rate. Federal spending and debt are at their highest share of the economy since World War II. America’s credit rating has been downgraded for the first time in our history.

So why does the 2012 election remain competitive?

First, despite their griping, Obama’s base still believes. Support among Democrats and African Americans is solid. Obama’s recent conversion to the old-time Democratic religion of class conflict — preached at Occupy Wall Street tent meetings — has rallied American liberalism. This approach has its limits. A message that shores up support from the left may complicate Obama’s appeal to independents. The construction of a 43 percent floor may also involve the construction of a ceiling not far above it. But Obama’s appeal to the political middle was no longer working. A base strategy was his only credible strategy, and it seems to have prevented a polling collapse.