President Obama's camp chafes at the notion the health care law's individual insurance mandate packs the threat of a tax. One way Democrats have been responding to to such criticisms is to point the finger at Mitt Romney and the health care law he signed as governor of Massachusetts.

"Let's get down to the bottom line here: Mitt Romney is the ObamaCare daddy," Sen. Richard Durbin, D-Ill., said on CBS's Face the Nation. "He gave birth to this baby up in Massachusetts, and now he doesn't recognize it."

President Obama made the same argument while on a bus tour last week, saying, "when you hear all these folks saying, oh, no, no, this is a tax, this is a burden on middle-class families, let me tell you, we know because the guy I'm running against tried this in Massachusetts and it's working just fine."

Analysts, however, say there are huge differences between ObamaCare and RomneyCare, and the biggest relates to taxes.