CHICAGO – Windy City Mayor Rahm Emanuel’s job approval ratings are continuing to circle the drain, and a new Chicago Tribune poll finds there’s a good chance he could lose next year’s election to Chicago Teachers Union President Karen Lewis, should she choose to run.

Lewis recently said the chances of her challenging Emanuel for the city’s top post in 2015 are “50-50,” but there’s little doubt that the mayor’s popularity problems are tipping the scales toward the affirmative.

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Emanuel’s job approval rating slipped from 50 percent just over a year ago to 35 percent in the most recent polling, which was conducted by APC Research for the Tribune through land line and cell phone interviews of about 800 city residents over the last week, according to the news site.

And for the first time in the Tribune’s polling history, more white voters disapprove than approve of Emanuel’s performance.

“In a May 2013 Tribune poll, 59 percent of white voters approved of the job Emanuel was doing. Now 44 percent approve. And those who disapproved of his job performance rose from 32 percent last year to 46 percent today,” the Tribune reports.

That reality spells trouble for the mayor, who has long relied on white voters for his base support. But black and Hispanic voters don’t think he is doing a very good job, either. His disapproval ratings among black residents increased from 48 percent in May 2013 to nearly 60 percent now. A majority of Hispanics approved of Emanuel’s work last year, but most disapprove today, according to the news site.

The mayor’s declining popularity is tied to criticisms about his handling of the city’s numerous problems, from crime to economic issues, but his education policy has drawn the biggest backlash. Emanuel’s decision to close 50 of the city’s most underutilized school buildings has drawn protests and scorn from the Chicago Teachers Union, which has painted Emanuel as “Mayor 1 Percent” and someone who puts business interests ahead of Chicago students, the Tribune reports.

The mayor’s unpopular education policy has also opened the door to a potential mayoral bid by CTU President Karen Lewis, who led Emanuel in a hypothetical matchup during the August polling.

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“In a head-to-head matchup, the survey found Lewis with 43 percent backing to 39 percent for Emanuel, with 14 percent undecided. Lewis’ advantage is just outside the 3.5 percentage point error margin for the poll …” according to the Tribune.

Lewis’ most significant political advantages are among the city’s black voters, union households, and public school parents. White voters were essentially split in their opinion of Lewis, though slightly more viewed her unfavorably.

“Black voters, meanwhile, considered the African-American union leader favorably – 46 percent, to only 13 percent unfavorably,” the Tribune reports. “Parents of (Chicago Public Schools) students who took part in the survey viewed her favorably by 49 percent to 19 percent who viewed her unfavorably.”

About 57 percent of CPS parents told pollsters they’d vote for Lewis over Emanuel, and 56 percent of union household members said the same.

That’s an interesting dynamic considering that Lewis is probably best known for leading the school district’s teachers on an eight-day strike in 2012, the first in 25 years.

Lewis is also a leading critic of the city’s charter schools, because most are non-unionized and pose a threat to the union’s monopoly on education.

The latest poll results will likely embolden Lewis, who has been publicly mulling a shot at mayor for weeks now. Emanuel’s crumbling favorability ratings show he’s vulnerable, but his bank account tells another story.

“Although (the polling) numbers are not a welcome sight for Emanuel as he seeks a second term, the mayor still has no significant declared opposition and has stockpiled $8.3 million in his campaign fund during an era of contribution limits. That would allow him to rebuild his image while defining eventual opponents to voters before they can define themselves,” the Tribune reports.

“Such a reality could chip away at Lewis’ support should she run.”