A very important vote in Chicago on Tuesday (quotes the head of DFER-IL):

Chicago Mayor Rahm Emanuel touts his education reform agenda as one of his greatest achievements as he campaigns for reelection.

It may also be his greatest vulnerability.

Emanuel is facing an unexpectedly tough challenge in his bid for a second term. Polls suggest his four opponents could pull enough votes in the Feb. 24 election to force a runoff.

That would be a political shocker, and it could reverberate far outside Chicago.

Democratic mayors and governors across the nation are increasingly standing up to their traditional allies in the teachers unions to demand huge changes in urban school districts — and labor is frantically, furiously fighting back. Local and national unions have made Emanuel a top target, pouring resources into the effort to oust him. If they succeed, they'll gain momentum, not to mention a huge PR victory.

But if Emanuel wins despite the unions' best efforts, analysts say it would embolden other Democratic reformers to forge ahead with a controversial agenda that includes closing struggling neighborhood schools, expanding privately run charter schools and overhauling the teaching profession by repealing tenure, trimming benefits and paying teachers in part based on how well their students score on standardized tests.

Portions of this agenda are already being championed by high-profile Democrats including New York Gov. Andrew Cuomo, Connecticut Gov. Dannel Malloy — and, most notably, by Emanuel's one-time boss in the White House, President Barack Obama. But the reform camp predicts more mayors, in particular, will be willing to jump into the fray if Emanuel proves that a big-city Democrat can defy the teachers union, anger a whole lot of black and Hispanic parents — and still pull off a win against liberal rivals in his own party.

"A lot of folks in the education debate are watching this race closely," said Owen Kilmer, who is running the political activities of Democrats for Education Reform Illinois, which supports Emanuel and his allies on the city council. "They want to know if education reform policies are going to succeed at the polls."