A small group of conservative lawmakers and legal scholars are focusing their anti-health-care energies on bringing the overhaul bill before the Supreme Court. Opponents think their last, best hope to stop the bill is to sue, and are arguing that the legislation’s mandate that people get insurance or pay a penalty is unconstitutional. The measure would not affect people who get insurance through their job, or are enrolled in Medicare or Medicaid, but it’s a key component of the Democrats’ plan because it pleases insurance companies, who will face new regulations under the bill. Although laws require drivers to buy car insurance, people can choose not to buy a car. There is no such alternative in the health-care mandate. “In the history of this country, the federal government has never required every American to enter into a contract with a private company,” said a co-author of a legal memorandum published by the Heritage Foundation.