WASHINGTON — The confidential memo from a former pollster for President Obama contained a blunt warning for Democrats.
Written this month with an eye toward Election Day, it predicted "crushing Democratic losses across the country" if the party did not do more to get black voters to the polls.
"African-American surge voters came out in force in 2008 and 2012, but they are not well positioned to do so again in 2014," Cornell Belcher, the pollster, wrote in the memo dated Oct. 1. "In fact, over half aren't even sure when the midterm elections are taking place."
Belcher's assessment points to an urgent imperative for Democrats: To keep Republicans from taking control of the Senate, as many are predicting, they need black voters in at least four key states. Yet the one politician guaranteed to generate enthusiasm among African-Americans is the same man many Democratic candidates want to avoid: Obama.
Now, Democrats are deploying other prominent black elected officials and other surrogates, buttressed by sophisticated voter targeting efforts, to stoke black turnout. At the White House, the president is waging an under-the-radar campaign, recording video advertisements, radio interviews, and telephone calls specifically targeting his loyal African-American base.
"Anybody who looks at the data realizes that if the black vote, and the brown vote, doesn't turn out, we can't win. It's just that simple," said Representative Marcia L. Fudge of Ohio, the chairwoman of the Congressional Black Caucus, referring to African-American and Latino voters. "If we don't turn out, we cannot hold the Senate."
African-Americans could help swing elections in Georgia, Louisiana, North Carolina, and possibly Arkansas, a New York Times analysis of voter data shows, but only if they turn out at higher-than-forecast rates. They will also be important in Kentucky, where Alison Lundergan Grimes, the Democratic Senate candidate, refuses to say whether she voted for Obama — a stance that black leaders including Fudge fear will depress turnout.
Republicans, who are expanding outreach to African-Americans in states like North Carolina and Georgia, have their own aggressive get-out-the-vote effort, mindful of the success of the Obama campaign, which turned out voters in record numbers.
Black voters made history in 2012, exit polling and census data show, when they turned out at a rate higher than whites to help reelect Obama. But fewer voters go to polls in midterm elections. In 2010, a disastrous year for Democrats, blacks voted at a rate lower than whites, creating a "turnout gap."
The numbers are significant. While more than 1.1 million black Georgians went to the polls in 2012, only about 741,000 voted in 2010. In North Carolina, Democrats say nearly 1 million black registered voters didn't vote in 2010.
Belcher declined to discuss whom he wrote the memo for, saying it was private, but the document was circulated by the Democratic National Committee. In the memo, he also asserted that the turnout gap, more than any Tea Party wave, was responsible for Democrats' 2010 defeats. So the challenge for Democrats is to get midterm voters to the polls at presidential election-year rates.
"If you tell me in Georgia that, on the closing of the polls, the electorate is 32 percent African-American, I'm going to tell you we have probably elected a Democratic senator," he said. "That's not theory. It's basic math."
But it is in no way easy. Sasha Issenberg, whose 2012 book, "The Victory Lab," explored the science of winning campaigns, said increasing turnout "is doable." But it is very expensive and time-consuming; on average, he said, a well-trained volunteer must have 14 contacts with prospective voters to produce one new vote.
Issenberg said his rough calculation showed that in Georgia alone, such an effort would cost $30 million. A national effort, he said, would be "resource-intensive on a scale that we've never seen executed in a midterm election."
Republicans are skeptical. "What the Democrats were able to pull off with African-American turnout in places like Ohio in 2012 was truly amazing," said Whit Ayres, a Republican pollster. "Accomplishing the same goal without the African-American president on the ballot at the top of the ticket is a totally different endeavor."
Still, Democrats are trying. The Democratic Senatorial Campaign Committee has poured $60 million this year into its Bannock Street Project, a data-driven effort to target potential voters, then make sure they vote.
In North Carolina, where Senator Kay Hagan is fighting to retain her seat, party field operatives have deputized more than 150 "captains" to help register voters. Nearly 30,000 African-Americans have registered since January.
In Georgia, where blacks make up 30 percent of registered voters, Democrats identified 600,000 unregistered black voters. The New Georgia Project, an officially nonpartisan effort founded by the Democratic leader of the State House, has helped register about 120,000 voters.