The Medicare plan in Ryan’s latest budget, which Romney says is “close to identical” to his own, has the details. In 10 years, Medicare would be remade into a subsidies system where seniors can buy insurance from a menu of private plans and a government option, with vouchers aimed at covering the cost of the cheapest two policies on the exchange.

That’s broadly similar to the core structure of Obamacare, under which the government sets up a regulated market exchange to ensure that plans cover a broad array of benefits. The law provides a subsidy to Americans who cannot afford insurance on their own.

Both plans also have mechanisms to compel people to participate: under Romney-Ryan, seniors are forced to pay Medicare taxes either way so they have no incentive not to use the voucher; under Obamacare, Americans either buy insurance or pay a tax penalty.