The Affordable Care Act, called "Obamacare" by its critics, is the subject of a challenge by 26 states to be heard by the U.S. Supreme Court this month. The national survey by the Pew Research Center for the People & the Press indicated 47 percent approve of the law, while 45 percent disapprove.
Back in January 2011, 41 percent approved and 48 percent disapproved, the survey said.
The survey said half of the U.S. public say Congress should either expand the healthcare law -- 33 percent -- or leave it alone -- 20 percent. Another 38 percent favor appeal.
When it comes to a key provision in the law requiring everyone to have health insurance by 2014 or pay a fine -- the individual mandate, which is the focus of the challenge before the Supreme Court -- 51 percent disapprove and 41 percent approve.
Support for the act divides along party lines. About 84 percent of Republicans disapprove of the 2010 law and 83 percent disapprove of the individual mandate. But three-quarters of Democrats, 76 percent, approve of the law and 66 approve of the individual mandate.
Independents also are divided -- 44 percent approve of the healthcare law, while 47 percent disapprove -- but 60 percent disapprove of the individual mandate.
Pew said most of the analysis in its report was based on telephone interviews conducted March 7-11 among a national sample of 1,503 adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia. The survey was conducted by interviewers at Princeton Data Source under the direction of Princeton Survey Research Associates International, Pew said.
Sample sizes and the error attributable to sampling shows what would be expected at the 95 percent level of confidence for different groups in the survey, the center said. There was no other margin of error listed.