Newt Gingrich voiced enthusiasm for Mitt Romney's Massachusetts health-care law when it was passed five years ago, the same plan he has been denouncing over the past few months as he campaigned for the Republican presidential nomination.

"The health bill that Governor Romney signed into law this month has tremendous potential to effect major change in the American health system," said an April 2006 newsletter published by Mr. Gingrich's former consulting company, the Center for Health Transformation.

The...