Few people know more about the pros and cons of universal health insurance than Mitt Romney. No longer a candidate for office, he has no reason to hedge on the subject. Speaking at a Long Island Association luncheon Wednesday, he made a crucial point about Obamacare and any plan Republicans might try to put in its place. He argued that Obamacare can only be replaced with plans that penalize those who don't sign up, as Obamacare does. He said, "We can't have large numbers of free riders."

While governor of Massachusetts a decade ago, Romney signed into law a system that covered practically everyone in the state. But while running for president, he had trouble explaining why he opposed a national system. In fact, he has a decent explanation: Massachusetts already had laws that said every health cost (he used in vitro fertilization as an example) must be covered in every policy. And 93 percent of the state's population had insurance before "Romneycare" took effect. So providing comprehensive insurance for everyone in Massachusetts wasn't the same heavy lift as doing so in states with big uninsured populations and less-comprehensive policies.

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Romney said different states can enact plans to replace Obamacare that we might learn from nationally. Provisions might include letting people buy catastrophic-care-only policies or plans that don't cover care they'll never need. Many Republicans mulling runs for president in 2016 would agree. But how many GOP candidates will admit that any plan must include the politically toxic mandate of insurance available to all, and can't allow "free riders" who don't enroll until they get sick?

Romney is an expert. He's also the most prominent Republican not running for president. When he points out what any Republican plan to replace Obamacare has to contain, we'd be wise to listen.