WASHINGTON — Has the U.S. achieved Martin Luther King Jr.’s dream of a colorblind society? Fewer than half of all Americans say the country has made substantial progress in the past 50 years toward racial equality, a new poll shows.

Despite a heightened sense of racial progress immediately following the 2008 election of the first black president, Americans’ views of black progress have waned.

The study, released Thursday by the Pew Research Center, offers a mixed picture of progress five decades after King made his historic “I Have a Dream” speech calling for racial equality. The center is a Washington-based research organization.

While large majorities of blacks and whites say the two races generally get along “very well” or “pretty well,” blacks continue to substantially lag whites when it comes to household income and net worth, and nearly 8 in 10 African-Americans say a lot of work remains to be done to reach racial equality.

Blacks are more likely than other race groups to say they have been discriminated against in the past year — 35 percent vs. 20 percent for Hispanics and 10 percent for whites — with majorities of blacks saying they are treated less fairly than whites in dealing with police, in the courts, in local public schools or on the job.

President Barack Obama’s 2008 election only temporarily boosted perceptions of progress for blacks. After initially rising across all races, the percentage saying blacks had gained ground in the last five years has dropped to levels last seen in 2007.

Only 1 in 4 African-Americans say the situation of black people is better now than five years ago, down from 39 percent in 2009. Among whites, it fell from 49 percent to 35 percent.

Overall, 49 percent of Americans say “a lot more” remains to be done to achieve racial equality. Among blacks, the share climbs to 79 percent, compared with 44 percent for whites and 48 percent for Hispanics.

“The public seems to be saying that we as a society are heading in the right direction, but we aren’t there yet,” said Pew senior editor Rich Morin.

Howard University sociologist Roderick Harrison, a former chief of racial statistics at the Census Bureau, said waning perceptions of black progress since Obama’s election reflect a bit of a reality check. The recent recession also hit blacks hard, particularly in employment, he said.

The Pew findings also coincide with an analysis by the AP-NORC Center showing optimism about the nation’s future divided by race as well as income and education levels, with blacks and Hispanics taking a more positive outlook than whites.

In the Pew survey, perceptions of economic disparity by race were less pronounced among those with lower income levels. Both blacks and whites with incomes below $50,000 annually were less likely than their higher-income counterparts to say blacks are worse off than whites. More than 40 percent of the poor are white.

Census data show that whites outpace blacks in median net worth — 14 to 1. In 2011, median black household income was 59 percent of median white income, up modestly from 55 percent in 1967.

Other findings:

—By political party, about 56 percent of Republicans say the U.S. has made a lot of progress toward racial equality, compared with just 38 percent of Democrats. When asked how much more needs to be done, 35 percent of Republicans say “a lot” compared with 63 percent of Democrats.

—About 7 in 10 blacks say they are treated less fairly than whites in dealing with police (70 percent) or in the courts (68 percent). And the Pew report shows that in 2010, black men were more than six times as likely as white men to be incarcerated. That’s up from 1960, when black men were five times more likely to be in a federal or state prison, or local jail.

— Blacks are more likely than other race groups to say they are treated less fairly than whites on the job (54 percent); in local public schools (51 percent); in getting health care (47 percent); when voting in elections (48 percent); and in stores or restaurants (44 percent).

The Pew survey includes interviews with 2,231 adults by cellphone or landline from Aug. 1-11, 2013, including 1,471 non-Hispanic whites, 376 non-Hispanic blacks and 218 Hispanics. Among all adults, the margin of sampling error is plus or minus 2.5 percentage points. It is higher for subgroups.