President Obama’s self-described “evolution” on same-sex marriage — from opponent to proponent — appears to be catalyzing a similar shift among some of his most loyal supporters, African-Americans. Although evidence for such a shift is preliminary — there are just a few data points and a number of caveats — Mr. Obama’s announcement may have accelerated the acceptance of gay marriage among blacks.

Support for same-sex marriage has been growing in the general population since at least the mid-1990s. That trend has been evident among blacks as well — but at a considerably slower pace. A poll conducted by Pew Research in April, just a few weeks before Mr. Obama’s announcement, found 39 percent of blacks supporting gay marriage and 49 percent opposing it. By contrast, a plurality of white Americans supported gay marriage in the Pew poll, as they have in most other recent surveys.

Since Mr. Obama declared his support for gay marriage, however, and similar pronouncements by the N.A.A.C.P, Jay-Z and Colin Powell, a handful of polls suggest that opinions in the African-American community are shifting.

An ABC News/Washington Post poll conducted May 17-20 found 59 percent of African-Americans in favor of same-sex marriage.

A Public Policy Polling survey in North Carolina, taken just after the state approved Amendment One, which prohibited both same-sex marriage and civil unions, found that black support for legalizing same-sex marriage or civil unions had increased 11 percentage points to 55 percent in favor and 39 percent against. A poll by the same group taken before Mr. Obama’s announcement — and before the voting in North Carolina — showed 44 percent of black respondents in favor of same-sex marriage or civil unions and 51 percent against.

In Maryland, a Public Policy Polling survey on a referendum on the state’s new law legalizing same-sex marriage found that black support for same-sex marriage had essentially flipped after Mr. Obama’s announcement. Support for same-sex marriage jumped from 39 percent to 55 percent, and opposition dropped from 56 percent to 36 percent. Both polls in Maryland were sponsored by Marylanders for Marriage Equality, which supports gay marriage.

There is reason to be cautious in interpreting these numbers. First, polling has tended to overestimate support for same-sex marriage ballot referendums by about seven percentage points. In addition, the sample sizes for demographic subgroups like African-Americans are small, producing large margins of error.

Moreover, voters who are newly converted to a candidate or cause may support only tenuously at first and may be persuaded to revert to their prior position. “People should expect a counterargument,” Andra Gillespie, an associate professor of political science at Emory University, said.

It may also be the case that Mr. Obama’s announcement did not change minds so much as it made it easier for African-American voters to express support for same-sex marriage publicly.

A study conducted last year by Melissa R. Michelson, a professor of political science at Menlo College in California, and Brian F. Harrison of Northwestern University, “It Does Matter if You’re Black or White: Race-of-Caller Effects on Black Support for Marriage Equality,” tested whether the race of the telephone interviewer made a difference in whether an African-American respondent would express support for same-sex marriage. As the study’s title suggests, it did.

“So if it was an African-American calling an African-American, then they were much more likely to say they were a supporter of same-sex marriage,” Professor Michelson said. “We don’t think people were changing their minds, but they felt more comfortable” expressing support for same-sex marriage.

At the very least, the signs of a jump in black support for gay marriage suggest that black voters are unlikely to abandon Mr. Obama over his same-sex marriage stance, as some commentators had predicted.

“I certainly want to see several more polls. But if these kinds of early signals are being sent, then we could see a significant transformation on same-sex marriage in the African-American community,” J. Michael Bitzer, a professor of political science at Catawba College in North Carolina, said.