Chicago's Mayor Rahm Emanuel attends an opening ceremony for the Yelp Inc. offices in Chicago on March 5. (Jim Young/Reuters)

Chicago Mayor Rahm Emanuel won every majority-black ward in the city when he was elected in 2011. But this week, a legion of black leaders rallied to the side of his insurgent liberal opponent, Jesus “Chuy” Garcia, underscoring the challenges Emanuel faces in his campaign for a second term.

The surprisingly competitive race between Emanuel and Garcia, which will culminate in an April 7 runoff election, has divided African Americans. The battle for black voters, which has ramped up in recent days, could decide the outcome of the race, close watchers say.

“What the mayor needs to get across the finish line is to pick up new voters. And I think the most promising sector of the electorate is the African American vote,” said Sen. Richard J. Durbin (D-Ill.), who supports Emanuel.

Both candidates hold unique advantages when it comes to black voters. Both also face distinct hurdles.

Emanuel has the support of President Obama, a beloved figure among African Americans in the city where he launched his political career. But it’s not clear that Obama’s backing will be enough to overcome black voters’ concerns about crime, education and the economy under Emanuel’s watch.

Chicago Mayoral candidate Jesus "Chuy" Garcia (standing) greets restaurant patrons, during a campaign stop in February in Chicago. (Jim Young/Reuters)

Garcia, a Cook County commissioner, has seized on those worries to build a coalition of black leaders, headlined by the Rev. Jesse L. Jackson and businessman Willie Wilson, the third-place finisher in the initial round of balloting. But there are questions about whether the complicated political history between blacks and Hispanics could ultimately hurt Garcia, who is Mexican American.

These variables are taking on more urgency for Garcia after a new poll out Friday suggested that Emanuel had seized the momentum in the race. A Chicago Tribune survey showed Emanuel leading 51 percent to 37 percent overall, with 11 percent undecided. It also showed the mayor leading among African American voters, 52 percent to 31 percent, with 15 percent undecided.

The Emanuel and Garcia campaigns declined requests for candidate interviews. Emanuel’s supporters pitched him as a leader willing to make tough decisions to turn the city around. Garcia’s backers said he offers a change of direction for a city in desperate need of a shake-up.

In the past six days, Garcia has unveiled a wave of endorsements from black leaders, including Wilson, Jackson and Rep. Danny K. Davis (D-Ill.). Wilson, a wealthy businessman, won about 11 percent of the vote Feb. 24, drawing much of his support from African Americans.

“Chuy Garcia is the only candidate in this race we can trust to put the needs of Chicago communities first,” Wilson said in a statement announcing his endorsement of Garcia.

Emanuel, who dramatically outspent the competition, led the way with 46 percent of the vote, short of the majority he needed to avoid a runoff against Garcia, who received 34 percent.

Support for the mayor among black voters was weaker than it was in 2011. He won 42 percent of the vote in majority-black wards, according to the Illinois Election Data Web site, which tracks voting patterns, down from 59 percent in 2011. Garcia took about a quarter of the vote in those wards.

With Emanuel expected to perform well in predominantly white areas and Garcia expected to win the Hispanic vote, the remaining third in those wards who voted for someone else could, depending on turnout, be vital.

Garcia has been hammering the mayor for closing 49 elementary schools; he has vowed to put more police officers on the streets to combat violent crime; and he is promising to shut down the city’s red-light cameras, which produce city revenue through fines.

Broadly, Garcia is trying to cast Emanuel as a champion of the city’s wealthy residents who has left lower- and middle-class neighborhoods behind. The underdog is also trying to form a variation of the so-called black-brown coalition that rallied behind Harold Washington, Chicago’s first black mayor and a Garcia ally, in the 1980s.

But in his efforts to make inroads with black voters, Garcia — who would be Chicago’s first Hispanic mayor — is also confronting the city’s history of strained relations between Latinos and blacks.

“The first rifts appeared soon after Washington’s death in 1987,” radio show host Salim Muwakkil wrote on the In These Times Web site this year. “When the black base split over which alderman should succeed Washington, Latino supporters were set adrift, and the remnants of the city’s infamous Democratic Machine exploited that uncertainty.”

Some say race will not be a dominant factor in the election.

“I think voters in Chicago have been willing to vote for a candidate regardless of their race or their background as long as their message is appealing to all the major blocs here,” said Tom Bowen, a former Emanuel aide.

Garcia is also running hard against Emanuel on crime, a tough area for the mayor to defend his record. While the number of homicides was the lowest in decades in 2014, the number of shootings went up.

“Murder capital of America was tagged to Chicago under this mayor’s administration,” the Rev. Ira Acree, a Garcia supporter, said at a news conference Wednesday.

Emanuel’s backers have fought the Garcia team’s attacks. One doubted the issue would resonate overwhelmingly with voters.

Alderman Will Burns, an Emanuel supporter, said, “I’m not saying that crime isn’t an issue in the winter, it’s just not as salient,” citing more violent crime in the summer months. “Talking about crime and homicides in the winter in Chicago is like talking about snow removal in August.”

Emanuel is touting the city’s raising of the minimum wage to $13 an hour by 2019 and its expansion of full-day kindergarten, arguing that he has put the city on a path for long-term economic success. The mayor’s campaign, which has outspent Garcia dramatically, has also slammed the challenger for failing to give details on how he would pay for the ambitious policies he is proposing.

Garcia released a fiscal blueprint Friday that said he would “have to look beyond efficiencies, beyond cost cutting and beyond diversions to our traditional sources of revenue.”

Emanuel’s campaign, which has already appeared to hint in a TV ad that Garcia would raise taxes, said the plan failed to address how the challenger would fund pensions and the budget.

Throughout the campaign, Emanuel has relied heavily on Obama, his former boss. The president has appeared in commercials for his first White House chief of staff, and he made an appearance in Chicago just days before the Feb. 24 election.

But it’s not clear whether Obama will return before the runoff. It’s also unclear whether even the nation’s first black president will be enough to guarantee Emanuel wins a majority of black voters, given the policy and style issues he’s had to address.

In a sign that Emanuel — whose nickname “Rahmbo” comes from his confrontational style — is trying to overcome worries about his brash image, he recently released a TV ad that sought to soften it a bit.

“I can rub people the wrong way, or talk when I should listen. I own that,” he says in the commercial.

In January, Emanuel unveiled the support of more than 200 African American leaders. He won the endorsement of Rep. Bobby L. Rush (D-Ill.), an influential South Side political figure, in February.

If Obama were to return before the election, it would be a sign the contest is competitive. If Emanuel has it locked up, there would be less reason for the White House to justify a trip; if Garcia had it in the bag, Obama would risk tethering himself to a losing campaign.

Emanuel’s campaign declined to comment on its outlook on the president’s plans. And neither campaign appears to be counting on the president to decide the race.

“Obviously, that’s helpful. But what I think is more important is to knock on doors and talk about the things Rahm Emanuel has done,” Burns said.