In Mitt Romney's 2010 book, No Apology, he discusses the "Medicare burden" and the challenge of dealing with the rising cost of health care entitlements. In the same section, it's something he claims to have been thinking about in a professional capacity for a long time: "When I was a young consultant to a health-care company in the late 1970s," he says in the book, "I predicted that health care would reach 20 percent of the GDP by 2050."

But apparently Romney wasn't thinking about it enough to grasp the differences between the two major health entitlements. In a campaign appearance in Iowa today, Romney told the crowd that he was unsure about all the distinctions between Medicare, the federal health entitlement seniors, and Medicaid, the jointly funded federal-state health program for the poor and disabled, until he started government work. “I have to admit I didn’t know all the differences between these things before I got into government,” Romney said, according to TPM. Romney didn't run for office until 1994, when he lost a Massachusetts Senate race to Ted Kennedy.  

As governor of Massachusetts, Romney figured out the difference soon enough: He relied on about $2 billion (so far) in bonus federal Medicaid funding to help pay for RomneyCare, his state-based health care expansion. But he still takes advantage of the fact that lots of voters share his early confusion. In this year's primary campaign, he's repeatedly criticized President Obama for cutting Medicare to pay for a federal health care expansion virtually identical in structure to RomneyCare without noting the federal Medicaid bonus that his Massachusetts still relies on. 

Update: As TPM's Benjy Sarlin points out, Romney also oversaw the purchase a $311 million hospital business while running Bain Capital in the 1980s.