With the advent of the Affordable Care Act, the share of Americans convinced that health care is a right shrank from a majority to a minority.

This shift in public opinion is a major victory for the Republican Party. It is part of a larger trend: a steady decline in support for redistributive government policies. Emmanuel Saez, an economics professor at Berkeley and one of the nation’s premier experts on inequality, is a co-author of a study that confirms this trend, which has been developing over the last four decades. A separate study, “The Structure of Inequality and Americans’ Attitudes Toward Redistribution,” found that as inequality increases, so does ideological conservatism in the electorate.

The erosion of the belief in health care as a government-protected right is perhaps the most dramatic reflection of these trends. In 2006, by a margin of more than two to one, 69-28, those surveyed by Gallup said that the federal government should guarantee health care coverage for all citizens of the United States. By late 2014, however, Gallup found that this percentage had fallen 24 points to 45 percent, while the percentage of respondents who said health care is not a federal responsibility nearly doubled to 52 percent.

Robert Blendon, a professor of health policy and political analysis at Harvard’s School of Public Health, wrote in an email that the character of the debate over health care began to change during the 2008 campaign. Before that, according to Blendon, the major issue was the moral principle of providing care for the poor. In the context of the presidential campaign, however, the public focus shifted:

Critics started raising concerns about the cost of these plans — higher taxes and premiums for those with coverage, more government interference in physician choices, and of course the potential of abortion coverage. People with coverage [83.7 percent of the population in 2010] became concerned about the implications for middle income people with these universal plans.

The altered public mood is especially relevant because the Supreme Court is expected to issue a ruling later this year in King v. Burwell, a case that challenges the legality of the Affordable Care Act.