WASHINGTON — On the day President Obama took the final step in turning the Affordable Care Act into law, his senior adviser, David Axelrod, predicted the public would eventually embrace his ambitious effort at health care reform.


“As the American people become familiar with what this program is and what it isn’t,” Mr. Axelrod said, “they’re going to be very, very happy with it.”


Two years later, the public is no happier with the law than it was then. Mr. Obama’s signature initiative may have prevailed in the Supreme Court, but a White House that vowed a public relations blitz selling the act’s virtues never fully followed through, much to the frustration of many Democrats and even some of the law’s authors.


Now Mr. Obama faces the consequences as he heads toward a hotly contested election that will decide whether he has a second term and, by extension, whether the law will survive efforts to repeal it.


And while the White House and its allies sent e-mails and held conference calls promoting the overhaul soon after the Supreme Court victory on Thursday, they privately made clear their interest in moving the national conversation back to the economy, the main electoral battleground.


“Unfortunately, we never had a really effective strategy around communicating to the public the benefits and the rationale behind health care reform,” said Ezekiel J. Emanuel, a physician and University of Pennsylvania vice provost who was a top White House adviser involved in developing the program. “We never had a spokesperson, and the public never really understood what we were doing.”


That failure still baffles supporters like Dr. Emanuel, given the significance of health care to Mr. Obama’s legacy. Some see it as a result of the president’s own instinctive diffidence or the natural desire to move to the next challenge. Others note the complexity of the act itself, or criticize the president’s advisers for not being more assertive.


But there was also calculation on the part of White House officials who concluded that the public was fatigued with the subject and more concerned about jobs. As they pondered plans to sell the overhaul, they found few troops to rally. Democratic lawmakers ran away from it and party donors refused to finance advertising to promote it.


“No one in history has ever been able to communicate successfully about health care, because it is a deeply personal and polarizing issue and people are therefore afraid of the unknown,” said Dan Pfeiffer, the White House communications director. “We need the law to be fully in effect before the known overtakes the unknown.”


Mr. Obama’s team holds out hope that with the validation of the court ruling, the health care law will generate more popular support as it is phased in through 2014. And they take heart from polls showing that elements of the law, like protections for those with pre-existing conditions, rate high with the public.


Some supporters have argued that other social programs in the past were controversial at first before becoming embedded in American society. But polling suggests that is not so.


Social Security was popular from the start, supported by 73 percent of Americans in early 1937 and 78 percent the next year in Gallup polls. Medicare had the approval of 62 percent in early 1965 and 82 percent by the end of that year in Harris polls.


By contrast, just 32 percent supported the Affordable Care Act when it was approved in March 2010, according to a New York Times/CBS News poll. As of a month ago, 34 percent supported it, virtually unchanged. To be sure, about a fifth of those who oppose it say it did not go far enough, essentially frustrated liberals.


That Mr. Obama’s presidency may be defined by the law would have seemed unlikely in March 2007, when as a presidential candidate he showed up for a health care forum in Las Vegas unprepared, by his own admission. When he finally developed a plan, he rejected requiring American adults to obtain health insurance and pilloried his chief opponent, Hillary Rodham Clinton, for supporting it.


As he took office, health care was on his agenda but not yet dominant. The economy was in a free-fall; health care competed with issues like climate change and immigration for Mr. Obama’s political capital. One adviser said if the White House had realized the economic troubles would be as sustained as they have been, health care might never have been on the table. Others disagree, arguing that health care did not detract from efforts to promote recovery.


Either way, health care rose to the fore in part through circumstance. The House passed a climate change bill, but it took deal-making and lobbying that alienated some around Mr. Obama. The White House concluded that the Senate could not pass the climate plan with only Democrats, since some from coal states opposed it. Likewise, Mr. Obama lost Republican cooperation on immigration, leaving health care the most plausible initiative.