The big news for Democrats is that the Daley brothers — Richard, who is the mayor of Chicago, and Bill — have been so fast to endorse Barack Obama in his bid to be president.

Both President Clinton and Senator Clinton are probably still adjusting to this sudden news. Mayor Daley has taken a neutral stance on other presidential elections; he could have done the same for this one. Especially since President Clinton made his brother Bill commerce secretary. Both Daleys have watched both Clintons work hard for years to prepare for Hillary’s 2008 run. Besides, unlike Mr. Obama, Hillary did spend her childhood in Chicagoland. She grew up in Park Ridge, west of Chicago’s city line.

Chicagoans are probably less shocked. And that’s not merely because Mr. Obama now represents Illinois as senator and Ms. Clinton, New York. Windy City citizens understand this race in their own context, that of a specific Illinois version of the political tradition of Old Democrat versus New Democrat.

The Daley family personifies Chicago’s Old Democrat tradition. First elected mayor in 1955, Richard J., the current mayor’s father, ruled Chicago for decades, building expressways, O’Hare Airport and the Sears Tower. Mr. Daley ran a political machine so corrupt and efficient that all Cleveland or Detroit could do was sit back and admire. Mr. Daley switched favorites in a minute if he thought someone had a better chance of pulling in votes. When he sent out the plows to clear his snowy city, Mr. Daley saw not blocks but blocs — voting blocs.

Mr. Daley could give as good as he got. The late columnist Mike Royko wrote in his biography, “Boss,” that “while Daley was mediating between white trade unions and black groups who wanted the unions to accept blacks, a young militant angrily rejected one of his suggestions and concluded ‘Up your ass.’ Daley leapt to his feet and answered ‘Up yours too.”‘ But the “boss” also was pragmatic. To Mr. Daley, like Hillary, ideology came second to dealmaking.

These attitudes left Mr. Daley unprepared for the mood of the Democratic National Convention in 1968, and the popularity of the anti-Vietnam War candidate, Eugene McCarthy. And it left him unready for demonstrators throwing garbage, bathroom tiles, even human feces at police. Mr. Daley’s police reacted strongly, even when the demonstrators weren’t violent, and made the additional mistake of attacking newsmen along with students. The brutal photos from the city’s lakefront forever marred Mr. Daley’s proud record. His sons both took note of that.

Illinois has another tradition into which Mr. Obama fits. It is that of the newcomer who changes the terms of the debate because of the sheer timeliness of his ideas. This tradition used to be inherent in the Republican Party. Abraham Lincoln rose this way, debating Stephen Douglas.

Lately the new prophets have been, mostly, Democrats. Paul Douglas, a senator of Spencer Tracy-level integrity, was an obscure labor economist at the University of Chicago when he first made his name in the 1930s fighting for unemployment insurance. Dan Walker, a corporate lawyer, claimed national prominence with a report that condemned Mr. Daley’s convention-week management as a “police riot,” — and won election as governor in 1972. The Walker style was later studied by a would-be governor of Arkansas, Bill Clinton.

Another outsider reformer was Abner Mikva, an anti-Daley Democrat who served in Congress from two different Illinois districts, and then as President Clinton’s White House counsel, and as a federal judge.

In recent decades many of these figures have been associated with Hyde Park, the South Side neighborhood that is home to the University of Chicago. Long before Washington thought about integration, Hyde Park did. Indeed one of the few places in America in which biracial couples like Mr. Obama’s parents felt at home in the 1960s was this tree-lined spot. This part of Chicago was post-racial decades before the label came to be used to describe Mr. Obama.

New Democrats spend relatively little time serving the party — Paul Douglas came not from the wards but from the classroom. They tend to be serious jurists — Mr. Mikva, Mr. Obama, once the editor of the Harvard Law Review. They are also true liberals in the sense that they fight more for the individual than the group.

And, finally, they are often pioneers, like Lincoln before them, when it comes to race questions. Mr. Obama’s refusal to blame the New Orleans flood deaths on racism would have pleased Douglas of Hyde Park, who, half a century ago, fought for integration of staff offices on Capitol Hill.

All of this history helps explain Hillary’s greatest advantage — her campaign war chest, the result of meticulous Daley-style tending of constituent groups. It explains Hillary’s popularity with Terry McAuliffe and other party leaders. She has done the national equivalent of Mr. Daley’s ward babysitting. It also explains why some blacks hesitate over Mr. Obama. Hillary is more likely to work with — some would say cater to — official black leadership.

Illinois history also explains the Daleys’ endorsement of Mr. Obama. The brothers learned not only from their father’s victories but also from his mistakes. They don’t want to look out of step with their times, as he did in 1968.

When it comes to general elections, Old Democrat often trumps New. If the Daleys are to prove they are as good at picking winners as their father generally was, they have to prove to themselves, Chicago, and the nation that Mr. Obama isn’t another George McGovern. One thing is already sure about Campaign 2008 —whatever political behavior we see this year, much of it was learned in Chicago.

Miss Shlaes is a visiting senior fellow at the Council on Foreign Relations and is a columnist for Bloomberg News.