In 1993 the conservative Heritage Foundation think tank fashioned a response to Bill Clinton's health care proposals. The key ingredient was a mandate to force everyone to buy health insurance to widen the risk pool and to bring younger healthier Americans into the pool to help bring down overall insurance costs. The Republicans adopted the Heritage Foundation's proposals as their response to the Clinton plan.
Clinton's plan went down in flames and health care has only got far more expensive and far more dysfunctional since then.
In 2006 as Governor, Mitt Romney supported legislation in Massachusetts which included the same mandate. Scott Brown, the state's new Senator supported the bill. Romney described the individual mandate as "a matter of personal responsibility", a principle revered by conservatives. Honesty, on the other hand, doesn't appear to be a conservative principle.
Now the Republicans are not only opposed to the mandate but are planning to challenge it based on constitutional grounds.
They are not interested in reforming health care. They believed they could defeat reform and hand Obama a humiliating victory. They lost and they will lose the battle to overturn or repeal the act. Polls since the vote show gains for Health Care Reform and for Obama. When people being polled are explained the features of Health Care Reform the majority approve. On some features approval is over 70%.
As Obama said, "Go for it."