In his first term, President Barack Obama made history. Now he has to make good. In 2010, Obama bested Theodore Roosevelt, Harry S. Truman, Richard Nixon and Bill Clinton by pushing through Congress a big health care reform law -- a sweeping measure that aims to extend coverage to at least 30 million of the country's 49 million uninsured. The Affordable Care Act, or Obamacare -- the president now says he likes the term -- since then has withstood relentless attacks from congressional Republicans, conservative governors, GOP presidential nominee Mitt Romney and even the Supreme Court. But none of those triumphs will mean a thing to the American people, especially the uninsured, if Obama can't meet the complex administrative and technical challenges involved in implementing the law or the job of selling it to those it aims to help. There is another threat as well.