A Tea Party member reaches for a pamphlet titled "The Impact of Obamacare", at a "Food for Free Minds Tea Party Rally" in Littleton, New Hampshire in this October 27, 2012 file photo. (REUTERS/Jessica Rinaldi//Files) (Jessica Rinaldi/Reuters)

Obamacare is a big deal for insurance companies. But you wouldn't know it from the ads they're running.

Despite the six-week-old health insurance marketplaces and their embattled federal Web site, HealthCare.gov, dominating the news, insurance companies have largely ignored the new health-care law in their advertising.

According to a study from Kantar Media CMAG, only one insurance company — Blue Cross Blue Shield — has made the new health-care law a centerpiece of its advertising campaign. Of the next four insurers who have run the most ads in recent months, only one has made even an implicit mention of the new law.

A single ad from Humana makes a glancing reference to a new "deadline" for people to obtain insurance. The other three in the top five — United Healthcare, Aflac and Cigna — haven't mentioned the new law even once in their ads.

Of more than $300 million spent on health insurance advertising since July 1, just about one-sixth of that — $55 million — has been spent on ads that explicitly or implicitly reference Obamacare. Since Oct. 1, about one-fifth of advertising makes reference to the health-care law.

It should be noted, though, that these numbers include advertising by the state-run exchanges and the Department of Health and Human Services, which are much more likely to advertise Obamacare. In other words, the percentage of insurers' ads that mention the law is likely much lower than even the numbers above suggest.

The reason isn't hard to suss out: This is a raw political issue, and even mentioning the law or acknowledging its existence is likely to rub its most strident opponents the wrong way.

The insurance companies, with the exception of Blue Cross, have simply opted not to even acknowledge the elephant in the room.