What would happen in 2016 if black voters were less than inspired by the Democratic nominee and reverted to their 2004 turnout level? Or if a 2016 Republican candidate once again won over just enough people in a few pivotal African-American communities? “To be sure,” Walter and Wasserman write, “a return to pre-2008 African-American turnout levels wouldn’t necessarily doom a Hillary Clinton candidacy, but it would leave her with a whole lot less margin for error in a host of swing states.”

I discussed Walter and Wasserman’s argument with several African-American political hands, all of whom concurred with the basic assessment. “I do think that the African-American vote may be the most important demographic as it relates to the presidential race,” said Doug Thornell, a longtime Hill staffer who is now the managing partner of the high-powered Washington-based communications firm SKDKnickerbocker. Thornell warned, however, that candidates asking for the black vote will not succeed by speaking in rosy platitudes.

“We did a poll last December in which African-Americans said that racism was the No. 1 issue in the country, ahead of the economy,” he told me. “So the critical thing for any of the candidates, Democratic or Republican, is that they’re going to have to talk about issues African-Americans really care about — things like economic opportunity, criminal-justice reform and voting rights. And it’s not just what they say at black churches or in front of the N.A.A.C.P. that counts. It’s also what they say in front of largely white audiences.”