When the Fair Housing Act first came into effect in the late 1960s and early '70s, a substantial share of white Americans supported the kind of discrimination the landmark law made illegal. They believed that whites had a right to keep blacks out of their neighborhoods. They said in surveys that they'd prefer a housing law that protected a homeowner's right to discriminate.

While that era sounds long ago, these positions took many years to shift. And that slow trajectory helps explain why there has long been little political will for the kind of desegregation — originally envisioned by the law — that the Obama administration now says it wants to enforce.

Since 1973, the General Social Survey has continuously asked whites which housing law they would vote for if they had two options: One saying a homeowner "can decide for himself whom to sell his house to, even if he prefers not to sell it to blacks," and another saying a homeowner "cannot refuse to sell to someone because of their race or color."

The second choice has been the law in America since the passage of the Fair Housing Act in 1968. But until the late 1980s, a majority of whites chose the first option:

The reversal over the last four decades has been striking. But as recently as 2014, 28 percent of whites still said they'd chose the law allowing homeowners to refuse to sell their homes to blacks.

On another GSS question, a third of whites in 1972 agreed with the statement "white people have a right to keep blacks out of their neighborhoods if they want to, and blacks should respect that."

When the GSS stopped asking the question in 1996, 12 percent agreed.

More recently, since just 1990, the share of whites who say they're opposed to living in a neighborhood where half their neighbors are black has fallen significantly, too:

Notably, the share of whites who'd favor living in such a neighborhood has remained relatively stable for the last 20 years. Alexander Polikoff, a long-time civil rights lawyer in Chicago, made this observation to me that may help explain that last picture: "It’s not that people in the large harbor racial animus, although there are some who do," he says. "It’s that people are fearful of inundation."

General Social Survey methodology

The General Social Survey was funded primarily by the National Science Foundation and conducted by NORC at the University of Chicago through in-person interviews with a random national sample of U.S. adults. The 2014 results for questions on housing laws and neighborhoods were based on 877 interviews non-Hispanic whites and have a margin of sampling error of plus or minus 4 percentage points. Previous year surveys interviewed between 504 and 1,352 whites, with error margins between 3.5 and 5.5 percentage points. Data were analyzed by The Washington Post.

Non-Hispanic whites were defined as respondents identifying their race as white  (RACE) and not identifying their ethnic origin (ETHNIC) as Mexican, Puerto Rican or "Other Spanish." This corresponds with Hispanic identity the vast majority of the time but allows for comparison of attitudes among non-Hispanic whites in years where Hispanic identity was not directly measured. Data are weighted to a composite weight which is the product of WTSSALL, FORMWT and OVERSAMP.

Question wording (questions asked separately in survey):  

Supposed there is a community-wide vote on the general housing issue. There are two possible laws to vote on. One law says that a homeowner can decide for himself whom to sell his house to, even if he prefers not to sell to (IF RESPONDENT IS NOT BLACK: blacks) The second law says that a homeowner cannot refuse to sell to someone because of their race or color. Which law would you vote for?

Here are some opinions other people have expressed in connection with (Black/African-American)-White relations. Which statement on the card comes closest to how you feel?

White people have a right to keep (Blacks/ African-Americans) out of their neighborhood if they want to, and (Blacks/African-Americans) should respect that right. Agree strongly, agree slightly, disagree slightly, disagree strongly, no opinion.

What about living in a neighborhood where half of your neighbors are Blacks (would you be very much in favor, somewhat in favor, neither in favor nor opposed, somewhat opposed, or much opposed)?

Scott Clement contributed to this report.