DES MOINES, Iowa — Democrats wasted no time looking for political opportunity after Donald Trump falsely accused Hillary Clinton of starting the rumor that President Barack Obama was not born in the U.S.

Just hours later, Rep. Hakeem Jeffries of New York was on Philadelphia R&B station, WDAS, critiquing Trump’s behavior. Days later Clinton’s North Carolina state organizers met in Raleigh, in part to chart how to use negative reaction to Trump’s statement to motivate the state’s disproportionately high black voting bloc to turn out. And Clinton’s team welcomed Georgia Rep. John Lewis, a civil rights activist, to a Philadelphia voter registration event where he railed against Trump’s claim.

Polls suggest Clinton can count on an overwhelming percentage of support from African-Americans. But she can’t necessarily count on them to vote.

“If they feel like they have the African-American community locked up, they should be very, very careful about making that assumption,” Sara Lomax Reese, president of Philadelphia’s independent black radio station WURD, said of Clinton and her team.

One of the biggest questions of the 2016 election is whether African-American voters will turn out for Clinton as they did for the first black president. They voted at a historic level in 2008 and an unexpectedly high rate in 2012.

Also to be seen is how political consequences play out over tensions between majority-white police departments and black communities, stirred by police shootings of African-Americans and ensuing unrest. Saturday marked the fifth day of rallies in Charlotte, North Carolina, since a black man was shot by police earlier in the week. Violence peaked Wednesday before the National Guard was called in the next day to maintain order.

Trump this month put to rest the myth he had peddled for years that Obama might have been born outside the U.S. But in the same breath, he said Clinton started it. In fact, she steered clear of the conspiracy theory when it bubbled up in the 2008 primary campaign and disregarded advice from her pollster to contrast her American roots favorably with Obama’s.

Although Clinton campaign aides said the birther issue would stay at the forefront in outreach to African-Americans and undecided voters, they declined to say whether they expected to run TV ads about it. The campaign did produce an online ad that could convert to a television spot.

Former Obama campaign pollster Paul Harstad said the added pressure, if kept up, could make a difference in competitive states with large segments of black voters.

“Trump further alienates blacks and gives them marginally more motivation to turn out, which could be a significant factor in close states like Ohio, Pennsylvania, Florida, North Carolina or Georgia,” he said.

It’s hard to know whether it’s worth spending the money to advertise about the issue because it’s uncharted territory, said University of Florida voter statistician Mike McDonald. “Romney and McCain didn’t go there,” McDonald said, referring to the two previous GOP presidential nominees who didn’t question Obama’s birthplace.

Seven in 10 blacks nationally say they would be afraid if Trump is elected, compared with 56 of all likely voters nationwide, in an Associated Press-GfK Poll taken Sept. 15-19. About two-thirds of African-Americans would be excited if Clinton is elected president, twice the percentage of all likely voters.

Mo Elleithee, a former Clinton adviser, said ads taking Trump to task on the birther issue might be worth it in states such as Pennsylvania and North Carolina if there’s a chance that would help Clinton even marginally increase her support from black voters. “They ought to make that play,” Elleithee said.