The survey of 1,543 registered voters also found that 72 percent of people are "unsure or mistaken" in their understanding of the tax. Just 28 percent were able to correctly identify it as a tax on "high-cost health plans."

A poll last month by the Kaiser Family Foundation also showed majority opposition (60 percent) to the tax. 

But the Kaiser poll also found that many could be influenced by an argument in favor of the tax. When told that the tax could slow the growth of health care costs, support jumped to 55 percent and opposition dropped to 30 percent. Conversely, respondents who were told that the tax might mean that employees would have to spend more out-of-pocket on health care opposed the measure by an even greater margin — 75 percent. 

Unions and employees that have negotiated for generous health benefits — often in lieu of wage hikes — fear that the tax will spur employers to shift health costs back onto the employer. Similarly, for employers that have opted to compensate employees with generous health benefits as a way to avoid taxes, the Cadillac tax means higher taxes, which businesses never like. 

Among the few supporters of the Cadillac tax are economists, who have long decried the tax exclusion carved out for health benefits more than half a century ago. That policy, they argue, has led to over-consumption of health care services that have led the cost of care to increase rapidly in recent decades.