When Mitt Romney left office as Massachusetts governor, his aides removed all emails from a server computer in the governor's office, and purchased and carted off hard drives from 17 state-owned personal computers, according to a current state official.

But a small cache of emails survived, including some that have never publicly surfaced surrounding Mr. Romney's efforts to pass his now-controversial health-care law. The emails show the Republican governor was closely engaged in negotiating details of the bill, working with top Democratic state leaders and drafting early copies of opinion articles backing it.

Mr. Romney and his aides, meanwhile, strongly . . . .