Even if he's not on the ballot, Rahm Emanuel will have played a heavy role in determining who becomes the next mayor of Chicago.

Emanuel's candidacy was invalidated on Monday by a state court, which ruled that he failed to meet Chicago's residency requirement, having lived in Washington, DC for the past two years as President Obama's chief of staff. Emanuel and his legal team will appeal the ruling to the state Supreme Court.

But while we wait for the final decision, it's worth noting that Rahm's candidacy has largely shaped this race. It's been the heaviest weight pulling on Chicago politics for the past few months, defining even the field of candidates.

By entering the race, Emanuel effectively forced several other top-tier candidates to drop out, simply by joining the contest as its perceived frontrunner. Now that he may be out of the race, Chicago voters are left with a field of candidates that's missing a couple prominent names.

When Emanuel left the White House on October 1 to run for mayor, Chicago political consultants and longtime observers weren't so sure he'd run away with the race. Cook County Sheriff Tom Dart, might actually be the favorite, one Chicago observer told me at the time. While most agreed that Emanuel had probably joined the race as its instant frontrunner, they all handicapped Dart as his stiffest competition. U.S. Rep. Luis Gutierrez's (D) name also surfaced on the short-list of serious contenders. Rep. Jesse Jackson, Jr. (D), another big name, was considered a long shot but also seen as someone who could command a significant power base and possibly influence the race.

After 27 days of Rahm's unofficial candidacy, Dart dropped out of the race. Gutierrez had decided against a bid two weeks earlier. Jackson, Jr. had come to the same decision one day earlier.

A goal for Rahm, Chicago political types told me when he entered, would be to craft a frontrunner image that would dissuade the competition (sort of like Hillary Clinton's perceived accrual of an "inevitability" aura in the 2008 Democratic primary)--in other words, to raise money fast and to scare away the competition. To let his rivals know that winning this race just got a lot tougher, and that they had just become underdogs.

If that's what Emanuel tried to do, he succeeded. He made a splash with his entrance, and his toughest competition faded away.

If Rahm had not entered this race, it's a safe bet that Tom Dart would be leading it right now. There wasn't much polling data available before Dart dropped out, but, by all accounts, he was in good position to open up a lead in this race.

Right now, former U.S. Sen. Carol Moseley Braun (D) and former public schools chief city community colleges chief Gery Chico rank second and third in the most recent Chicago Tribune/WGN poll, respectively. Emanuel took 44 percent; Braun took 21 percent; Chico took 16 percent.

In October, neither Braun nor Chico were considered heavy contenders. Now, either of them could win it.

So if he is forced out, Rahm will have left this race in very different shape than he found it. Some one-time contenders may be kicking themselves right now, and Chicago's next mayor--if it's not Emanuel--will probably have Emanuel to thank.