The preliminary Reuters / University of Michigan consumer sentiment index for March declined to 71.8 from the February reading of 77.6.
This was well below the consensus forecast of 77.7, and very low. There are a number of factors that impact sentiment including unemployment, gasoline prices and, for 2013, the payroll tax increase and even politics (sequestration, default threats, etc).
In this case, the decline was probably related to both high gasoline prices and policy concerns. According to Reuters, a record 34 percent of those surveyed were negative about government economic policies (sequestration, etc.). Reuters also reports that buying plans were essentially unchanged.