John McCain's plan for a healthcare system built around consumers shopping for their own insurance comes would bolster the role of high-risk pools, which sell insurance to people with pre-existing conditions such as diabetes, cancer and AIDS. These pools require significant government subsidies, charge high premiums and sometimes sharply restrict benefits or enrollment. Nationally, fewer than 200,000 people are enrolled in such pools, while 47 million people in the U.S. are without insurance.