Kantar Media's Campaign Media Analysis Group, which monitors political advertising, says that more than $500 million has been spent on Obamacare-related political advertising since the program became law in 2010.

Anti-Obamacare ads have outnumbered supportive messages by more than a 4-to-1 ratio, Kantar says. Analysts say the massive spending by Obamacare foes has contributed to Obamacare's shaky showing in recent opinion polls.

New Reuters/Ipsos polling data showed Tuesday that 46 percent of Americans disapproved of Obama's handling of the healthcare overhaul, passed by Congress four years ago.

Up to now, disapproval rates have not reflected the views of younger adults who could benefit from Obamacare. But over the summer, Obamacare's foes began targeting two major demographic targets for the administration: young people and women.

Generation Opportunity, a conservative group that appeals to the young, has two "Creepy Uncle Sam" videos that picture young Obamacare enrollees being confronted in a medical examination room by a sinister-looking Uncle Sam. In one, a smiling Uncle Sam startles a young woman during a gynecological exam.

"Don't let government play doctor," the video warns. "Opt out of Obamacare."

The same group intends to hold anti-Obamacare events on 20 college campuses in the coming months.

Americans for Prosperity, another conservative group, has spent millions on television ads in selected states that show mothers and other women worrying about whether their healthcare will suffer with the government "in the middle of things."

But opposition ads may have difficulty short-circuiting the Obamacare campaign, which will rely heavily on alternative channels such as the Spanish-language cable channel Univision, African-American radio stations, and the social media Web sites Facebook and Twitter.

Many of the administration's marketing targets are similar to those in Obama's 2012 re-election campaign.

"The Obama campaign proved in 2012 that they could defy everyone's expectations by turning out unexpectedly large numbers of young people and Latinos. They're certainly justified in feeling confident that they can do it again," said Elizabeth Wilner of the Campaign Media Analysis Group.

The White House's biggest hurdle could be informing people that benefits exist. Only about half of those who would gain coverage know about the benefits, organizers say, adding that most new enrollees may not sign up until 2014.

Others disagree, saying the rollout may do well in the 16 states that have their own healthcare marketplaces, including California, but that things might not go as well in conservative "Red" states such as Texas.

"California and Texas will look like different countries where healthcare's concerned," said Robert Blendon, who tracks the politics of healthcare at Harvard University.

"This is a local implementation issue," Blendon said. "It's not a president, first lady, Joe Biden issue. But they don't know what else to do, so they're going with the army they've got, and that's what they know from elections."