He has already raised more than $10 million. Last week he stood on a stage in the city's cultural centre as the big dog – Bill Clinton – spoke to a capacity crowd to offer his all-important endorsement. He has even endured the first of several planned televised debates with his opponents for the job that he wants and thinks he deserves.
But Rahm Emanuel, a former adviser to Mr Clinton and more recently chief of staff to President Barack Obama, has abruptly run into the buffers in his campaign to become the next mayor of Chicago. The culprit is a question that has been quietly stalking him from the start – after all that time in Washington does he still qualify as a Chicago resident?
Yesterday the Illinois Appellate Court ruled that, no, he does not. More gravely, it said that Mr Emanuel must be removed from the ballots when the city votes on a replacement for Mayor Richard Daley next month. While it was a divided ruling – one of three judges dissented – the implications for Mr Emanuel could be disastrous.
His campaign had already signalled last week, however, that in the event of a ruling against them, they would automatically appeal the case to the Illinois Supreme Court.
It was a sudden, possibly temporary, reversal for Mr Emanuel who has consistently argued that he maintained his home in Chicago, paid taxes on it and voted in Chicago.
And if he indeed spent long periods in Washington DC it was to offer national service, he said. He therefore should not be penalised for it.
At various turns over recent weeks, Mr Emanuel seemed to be winning the argument. The Chicago elections board agreed with him and so more recently did a judge in Cook County which is home to the city.
It is not an issue, however, that his three opponents – Miguel del Valle, former US Senator Carol Moseley Braun and Gery Chico – wanted to see so easily settled. Every poll has shown Mr Emanuel easily winning the race, assuming he is allowed finally to run.
On a straightforward reading, the rules say that any candidate running to be mayor of the Windy City must have been living there for one calendar year before polling day. Mr Emanuel resigned from his position as White House Chief of Staff in October last year only.
The most recent poll in Chicago released over the weekend showed Mr Emanuel, who has a reputation for strong language and even stronger political tactics, easily leading the field. He had the support of 44 per cent of likely voters with Ms Moseley Braun, who is African American, taking 21 per cent and Mr Chico, the President of the Board of Education, with 16 per cent. No one else achieved double digits.
Guaranteed now is a high-octane legal showdown in the Supreme Court in the state capital, Springfield. And the time pressure is intense, with only a few weeks remaining before polling day.
Seen by some as an arrogant and overweening figure, Mr Emanuel is not a man used to personal setbacks. It was an open secret for months while he was still serving Mr Obama as Chief of Staff, that he was coveting the job of running one of America's biggest and most vibrant cities. He left Washington with the unspoken endorsement of the president, even though he had not made any commitments personally to campaign for him.
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