Among all registered voters, support for the law rose to 48% in the online survey conducted after Thursday's ruling, up from 43% before the court decision. Opposition slipped to 52% from 57%.

The survey showed increased backing from Republicans and, crucially, the political independents whose support will be essential to winning the November 6 presidential election.

Thirty-eight percent of independents supported the healthcare overhaul. That was up from 27% from a Reuters/Ipsos poll taken days before the justices' ruling. Opposition among independents was 62%, versus 73% earlier.

"This is a win for Obama. This is his bill. There's not really any doubt in people's minds that it belongs to him," said Julia Clark, vice president at Ipsos Public Affairs. "It's his baby. It's literally been labeled 'Obamacare' ... which maybe it works in his favor now that there's a little bit of a victory dance going on."

Republican opposition to the law stayed strong, if somewhat weaker than before the high court ruled. Eighty-one percent of Republicans opposed it in the most recent survey, down from 86% in the poll conducted June 19-23. In the earlier poll, 14% of Republicans supported the healthcare plan, compared to 19% in the more recent one.

Illustrating the political polarization on the issue, three-quarters of Democrats backed the law, the same as a week earlier. One quarter opposed it.

The two top Republicans in Congress vowed on Sunday to push ahead with efforts to repeal the law despite the Supreme Court upholding it, but the White House said it is time to stop fighting and start implementing it.

Fanning opposition's flame

In some good news for Republicans, the Supreme Court ruling is energizing opposition to the 2010 healthcare law.

In the new poll, more than half of all registered voters (53%) said they were more likely to vote for their member of Congress if he were running on a platform calling for repeal, up from 46% before the ruling.

"This is galvanizing both sides," Clark said.

Obama's Republican challenger, Mitt Romney, has made it clear that he will run against "Obamacare." Within hours of the Supreme Court's ruling, the former Massachusetts governor asked voters to throw Obama out of office to get rid of the law, which he promises to repeal and replace if he wins the White House in November.

There have been some early signs that the appeal is working. On Friday, Romney's campaign said the former Massachusetts governor raised $4.6 million in the 24 hours following the Supreme Court's decision.

Romney has offered few specifics on how he would replace the Obama reforms, although he said he would work to retain popular provisions such as blocking insurance companies from forbidding coverage of patients with pre-existing medical conditions.

The Reuters/Ipsos poll showed little change in the strong support for that and most of the other major provisions of the bill, including requiring companies with more than 50 employees to provide insurance for their employees and allowing children to stay on their parents' insurance until age 26.

Most Americans still oppose the law's "individual mandate" requirement that most people obtain health insurance by 2014 or face a penalty, which the Supreme Court found was constitutional under the government's power to impose taxes.

Despite the court labeling the mandate a tax -- which Republicans have seized on in campaigning against Obama -- the new survey found support for it unchanged. Thirty nine percent of all Americans backed the mandate, compared with 61% who opposed it.

The survey interviewed 991 Americans online from June 28-30. The precision of the Reuters/Ipsos online polls is measured using a credibility interval. In this case, the poll has a credibility interval of plus or minus 3.6 percentage points.

By Patricia Zengerle

Last Updated: 2012-07-02 10:25:25 -0400 (Reuters Health)

Copyright © 2012 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.

Court decision great news for older Americans, June 29, 2012

Supreme Court upholds Affordable Care Act, individual mandate, June 28, 2012

Supreme Court healthcare decision expected June 28, June 25, 2012

Healthcare court ruling could paralyze Medicare, June 5, 2012

Obama confident top court will uphold healthcare law, April 3, 2012