Now that the race for the Democratic presidential nomination has moved into close-quarters combat for delegates, analysts will search for the cunning strategies or the mistakes that win or lose elections. But when I look at the race, I am reminded of the role played by chance and unforeseen consequences.

I spent the 1998 election night at the headquarters of the Cook County Central Committee (to specify Democratic in Chicago is superfluous). That famous "smoke-filled room" had been defogged by no-smoking building rules, leaving men and women to suck on mints and mutter into cell phones as they watched the returns come in.

The incumbent Democratic U.S. senator, Carol Moseley Braun, was losing. Democrats across the country had managed to hold on to their edge in the Senate despite — or perhaps because of — the bitter inquisition into President Clinton's high jinks with a White House intern. But many Illinois Democrats found it harder to defend Moseley Braun against alleged corruption charges. Some committee members told me they had been eager to find a candidate to run against the senator in the primary. But open opposition was risky. They didn't want it to look as if the Democratic Party would scuttle a figure from history — her election as the first black woman in the Senate had been a source of pride for the state.

They mentioned the names of several black officeholders who had been carefully contacted to be potential candidates. But none had leaped at the chance to run against someone whose portrait hung in school classrooms. No one mentioned the name of Barack Obama.

Then someone said that someone had called Hillary Rodham Clinton. Reports that she was interested in running for the U.S. Senate somewhere had first appeared in 1997. But committee members said that she had politely declined even a tickle of interest from her old home state. We can only speculate why. After all, 1998 abounded with investigations (Paula! Troopergate! Monica!) into President Clinton's behavior. Hillary Clinton would have had personal and political reasons to stay close to her husband and daughter in the White House. She might have been sick of politics. She might have dreamed of starting a fresh life in New York. But she might also have wanted to avoid beginning her electoral career running against an important symbol in black and women's history.

Yet had she run, I think Hillary Clinton would have been elected senator from Illinois in 1998. And Obama, who wound up winning that seat in 2004, would not now be running against her for president.

Obama was demonstrably ambitious. He served just a term in the Illinois Senate before running in the Democratic primary for Rep. Bobby Rush's seat in 2000. That campaign featured some ugly racial undertones, portraying Obama as an academic lakefront liberal who was African, not African American, and who hadn't shared the experience of being truly black in Chicago's inner city.

He lost by a wide margin — luckily for him. Had Obama won that primary, he would be a junior member of the Illinois congressional delegation today and identified as winning a "black" seat in an urban district. His eloquence and political skills would get him mentioned as a possible candidate for mayor or secretary of state (but the one who signs motor vehicle licenses and flies off to Bloomington and Rantoul, not Paris and Rome).

Instead, Obama is now vying with Clinton for president. It is irresistible to contemplate the turns that history just misses taking through our lives. What if Hillary Rodham had fallen in love with another one of her Yale Law classmates — say, Stephen Hadley, President Bush's national security adviser? Or economist Robert Reich? Or, for that matter, some guy she met on the slime line while working at a fish cannery in Alaska the summer after graduating from Wellesley?

And what if Obama had headed for New York after Harvard, rather than Chicago? What chance would he have had to win state office if he had to elbow for position among Al Sharpton, Andrew Cuomo, Robert Kennedy Jr., Eliot Spitzer — and Clinton?

I think Clinton is less scheming than her detractors suppose, and Obama may be more calculating than many of his admirers appreciate. I don't think that a young woman of allegedly ruthless ambition would leave Washington to marry a man in a small Arkansas town who had just lost a race for Congress. I also don't think that someone who was Harvard Law Review president didn't make a series of deliberate choices to put himself in a position to one day run for high office. And why not?

Each chose to build a base in a place that could support their ambitions. But no decision they made could succeed without the hand of chance, including the race she spurned, and the one he ran and lost.

Scott Simon is the host of NPR's "Weekend Edition." He wrote this commentary for the Los Angeles Times.