An illustrative example from this morning's Washington Post column by Charles Krauthammer:

Obama [suggested] that his health-care reform was indeed popular because when you ask people about individual items (for example, eliminating exclusions for pre-existing conditions or capping individual out-of-pocket payments), they are in favor.
Yet mystifyingly they oppose the whole package. How can that be?
Allow me to demystify. Imagine a bill granting every American a free federally delivered ice cream every Sunday morning. Provision 2: steak on Monday, also home delivered. Provision 3: A dozen red roses every Tuesday. You get the idea. Would each individual provision be popular in the polls? Of course.

However — life is a vale of howevers — suppose these provisions were bundled into a bill that also spelled out how the goodies are to be paid for and managed — say, half a trillion dollars in new taxes, half a trillion in Medicare cuts (cuts not to keep Medicare solvent but to pay for the ice cream, steak, and flowers), 118 new boards and commissions to administer the bounty-giving, and government regulation dictating, for example, how your steak was to be cooked. How do you think this would poll?

More wisdom and wit here.