Mitt Romney travels to Ann Arbor today to deliver what his campaign bills as a major address laying out his "2012 principles for health-care reform." These are likely to be sensible, but what we'll be listening for is how he explains his health-care principles of five years ago.

As everyone knows, the health reform Mr. Romney passed in 2006 as Massachusetts Governor was the prototype for President Obama's version and gave national health care a huge political boost. Mr. Romney now claims ObamaCare should be repealed, but his failure to explain his own role or admit any errors suggests serious flaws both in his candidacy and as a potential President.

There's a lot to learn from the failure of the ObamaCare model that began in Massachusetts, which is now moving to impose...