The chart below comes via Gallup:
By contrast, Democrats' top concern was the dysfunctional government, at 16 percent, followed by the economy, at 13 percent. Immigration was fourth on the list, at 11 percent.
The survey comes in the wake of an influx of thousands of unaccompanied Central American children who have been apprehended at the southwest border. It also comes ahead of an expected executive action by President Barack Obama which is expected to include deportation relief for some undocumented immigrants who have been living in the United States.