President Obama's attempt to dramatically expand the healthcare system has attracted support from insurers, hospitals, and other players in the powerful medical lobby who are set to participate in an unusual White House summit on the issue. The lure for the industry is the prospect of tens of millions of new customers: If Obama succeeds in fulfilling his pledge to cover many more Americans, those newly insured people will get checkups, purchase medicine, undergo physical therapy, and get surgeries they cannot afford today.