There is a dual purpose behind Cook County Circuit Court Clerk Dorothy Brown's 2007 candidacy for mayor. Ostensibly, she wants the job, but in reality, even if she loses, she is positioning herself to be the city's most influential black politician . . . and to make another race in 2011.

Brown's bid completely transforms the racial dynamics of the contest. Now, U.S. Representative Jesse Jackson, Jr. (D-2) must run, if only to make himself Chicago's number one black politician and to pre-empt Brown's effort. And, with two black candidates in the race, U.S. Representative Luis Gutierrez (D-4) surely will run, figuring he might finish in second place.

With three credible, well funded candidates opposing Mayor Rich Daley in the Feb. 27, 2007, election, Daley likely will be held under 50 percent of the vote, assuring an April 4 runoff. With three anti-Daley candidates pounding the mayor's performance and seeking to create their own constituency, a huge turnout is assured, especially among anti-Daley and minority voters.

And, with Gutierrez trying to build a liberal white-Hispanic coalition while Brown and Jackson focus on turning out the black vote, there will be enormous pressure on Daley to crank out an overwhelming white vote. But with the Hired Truck scandals having resulted in 41 convictions to date and the federal investigation continuing, Daley's ability to dispatch hundreds of city workers into targeted wards has been effectively neutralized, and city and county workers may be less than industrious in their precincts.

Furthermore, Daley is not facing an inconsequential foe. In 2003 the Reverend Paul Jakes got 14 percent of the vote. Dock Walls, a former Harold Washington aide, was the only announced candidate for 2007 until recently. Now media attention and scrutiny will be intense, with the focus being on City Hall scandals, not race. Instead of stories about whether Chicago will have a black or Hispanic mayor, the media buzz will be about whether the iconic Daley can survive his scandals.

Expect Brown, Jackson and Gutierrez to position themselves as reformers and agents of change. Since his initial election in 1989, Daley, age 64, has nibbled away at the black vote and has gotten the bulk of the Hispanic vote. For 2007 it will be the reverse: The "Big Three" of Jackson, Brown and Gutierrez will be nibbling away at the white vote, attempting to corral those white voters, particularly those along the Lakefront, who are disenchanted with city scandals.

The demographic reality in Chicago is that the white population is stable, the Hispanic population is exploding, and the black population is declining. The proportions in the 2000 census were 44 percent white, 37 percent black and 19 percent Hispanic.

The electoral reality is that whites constitute 45 percent of the voting population, blacks 43 percent and Hispanics just 14 percent.

But the political reality is that Hispanics don't want a black mayor, as that might preclude a Hispanic mayor in the future. Blacks don't want a Hispanic mayor, as that might preclude a future black mayor. And ethnic and Northwest Side and Southwest Side whites would rather have an ethically challenged white mayor than a minority mayor.

  As always, turnout is critical. Daley has habitually gotten more than 90 percent of the white vote, two-thirds of the Hispanic vote and a growing black vote. He won all 50 wards against Jakes in 2003 and got 63 percent of the black vote

That won't happen in 2007, because turnout will be much higher. Daley first ran for mayor in 1983, getting 343,506 votes (29.8 percent of the total cast) and finishing behind Jane Byrne (33.6 percent) and Harold Washington (36.3 percent). Turnout that year was 1.2 million, and Daley was deemed the "spoiler." In 1987, when Washington beat Byrne again, turnout was 1.1 million. In 1989, after Washington's death, turnout dropped to 900,000 and Daley got 486,586 votes in the primary (55.4 percent of the total) and 574,619 votes in the election (56.1 percent). In 1991 turnout dropped to 650,000 and Daley got 407,770 votes in the primary (63 percent) and 450,155 votes in the election (71 percent).

In 1995 turnout dropped again, to 500,000, and Daley got 336,183 votes (66.3 percent) in the primary and 350,785 (60.1 percent) in the election. In 1999, after the General Assembly abolished primaries and mandated a nonpartisan election, turnout was 550,000 and Daley got 418,211 votes (72 percent). And in 2003 turnout was 425,000 and Daley got 347,698 votes (79 percent).

Voter registration in 2004 was 1,416,101, and turnout for the fall election was 1,063,860 (75.1 percent). Jackson talks about a major black voter registration effort, in the realm of 600,000, but that's nonsense. The voters are there. Registration in 2004 in Chicago's 20 black-majority wards was 631,920, and turnout was 461,930, or about 73 percent.

However citywide turnout in 2003 was just 442,783, or 600,000 lower than in 2004, while in the black-majority wards it was just 181,185, or barely 28.7 percent, and Daley got 115,149 votes, or 63.5 percent of the total.

For 2007, three developments are clear. First, Jackson or Brown must engender a 2004-like black turnout, somewhere around 500,000. Second, black voters must opt overwhelmingly for a black contender, which could clip more than 100,000 votes from Daley in the black wards. That would reduce Daley's 2003 vote of 347,698 by nearly a third.

And third, one of the two must emerge as the "Great Black Hope," energizing the black base and taking two-thirds (or at least 300,000) of that vote. Since Brown announced first, her backers will use the term "spoiler" when Jackson jumps in. Both are South Siders, and both have strengths. Brown has been the court clerk since 2000, and she controls more than 2,000 jobs. Jackson has been a congressman since 1995, and he is a compelling orator and will have unlimited funding, thanks to the connections of his famous father.

Expect 2007 turnout to be in the realm of one million. That leaves about 500,000 votes for Daley and Gutierrez to divide.

Voter registration in Chicago's nine Hispanic-majority wards is 190,117, but the turnout in 2004 was just 123,226. Gutierrez, who once was an ally of Harold Washington, now is reviled by many black voters because he defected to Daley in 1989 and has backed the mayor since. He will get few black votes. As a Puerto Rican, Gutierrez is not close to the Mexican-American politicians who rule the South Side Hispanic wards and who would rather see Daley win again than have Gutierrez in City Hall.

To be competitive, Gutierrez would need at least 90 percent of the citywide Hispanic vote, plus the votes of another 100,000 white liberals. The embattled Hispanic Democratic Organization proved in the 2006 primary that it is not defunct, but Gutierrez looks like a fourth-place finisher.

A Chicago Tribune poll in February found that 56 percent of Chicagoans approve of Daley's performance and that 70 percent believe that he knew about corruption in city hiring. That's not encouraging for the mayor.

Registration in Chicago's 21 white-majority wards is 594,064, and the turnout in 2004 was 478,704. In past mayoral elections, white voters on the Northwest Side and Southwest Side and independent-minded and liberal voters along the Lakefront overwhelmingly backed Daley, but as the turnout has declined in mayoral elections since 1989, so has Daley's vote: 574,619 in 1989, 450,155 in 1991, 350,785 in 1995, 418,211 in 1999 and 347,698 in 2003.

In fact, Daley's 2003 vote of 347,698, which was 79 percent of the votes cast, barely topped his 1983 vote of 343,506, which was 29.8 percent of the total.

Turnout surely will be way up in 2007, and the question is how far down Daley's vote will plunge. With Brown and Jackson battling for the black vote, they will have little time or money to appeal to white voters. However, if one of them emerges as the major anti-Daley contender, that could change. If the white turnout in 2007 hits 450,000, at least 100,000 of those voters likely will opt to vote against Daley, perhaps as many as 150,000. Will they gravitate to Gutierrez or to Jackson?

For Daley, his numbers are critical both psychologically and in actuality.

On Feb. 27 he needs 450,000 votes. That means 90 percent of the white vote, 70 percent of the Hispanic vote, and 10 percent of the black vote. That won't happen. Daley will not be re-elected in the first vote.

But he needs to come close to 50 percent. How would it look if an 18-year mayor with a magic name gets barely 40 percent of the vote or less? With three formidable foes, it is entirely possible that they could collectively amass more than 60 percent.

But Daley will finish first, and he has one huge advantage: Whoever finishes second will not have the backing of the third- and fourth-place finishers. If it's Daley-Jackson in April, Brown and Gutierrez will offer no aid to Jackson. Ditto if it's Brown or Gutierrez against Daley.

Going into 2007, Daley ranks as the favorite to win another term, but it will be a nasty, ugly victory.