In the fall of 2007, Sen. Hillary Rodham Clinton had a 2-1 lead over the rest of the Democratic field combined. Less than eight months later, she conceded defeat to Sen. Barack Obama after finishing a close second.

What happened?

There were three key mistakes that caused her defeat: strategic, tactical and, most importantly, organizational.

In fairness to Clinton, she lost to a very naturally gifted candidate, a man who may be the next JFK or the Democratic Ronald Reagan. It was certainly no shame. But in any contest where an upset happens, the question must be asked: Did the favorite give it away or did the underdog take it away by performing unexpectedly well?

Given that Obama won a primary record of nearly 18 million votes, we would have to say that he won, not that Clinton booted it away. In 2004, John Kerry romped through the primaries with 9.9 million votes. In a normal year, against a less-talented, less-popular opponent, Clinton’s 17.5 million votes would have been a landslide.

All through 2007, Clinton averaged roughly 45 percent in the national Gallup preference polls among Democrats despite the fact that she had 100 percent name recognition. Since she was below 50 percent, that meant she was vulnerable if a single opponent could consolidate the majority of Democrats who were not for her in 2007. That is pretty much how the primaries unfolded: after John Edwards and the rest of the field collapsed in January, Obama was able to unite the anti-Hillary vote.

She won 48 percent of the national vote, very close to her 2007 average in the Gallup Polls. But Obama won slightly more votes (48.1 percent) in the closest primary contest ever. In short, there were strong negative feelings about her, and Obama was able to capitalize on them. So that’s how it happened. Here’s why it happened:

The strategic mistakes by Clinton were overconfidence and taking her opponent too lightly. This was a classic front-runner’s error. Nor was she alone in making this mistake: Since the Democratic nomination process shifted to a reliance on primaries in 1972 instead of being decided in back rooms at the convention, numerous front-runners have been upset: Ed Muskie, Henry Jackson, Ted Kennedy, Gary Hart, Bob Kerrey, Howard Dean. Walter Mondale and Al Gore, who both served as vice president, have been the only two Democratic front-runners to win contested nominations since 1970.

Republicans are like a business: They generally promote from within. Democrats, as the party of social change, usually don't go for the argument, "it's my turn now." After eight long years of George W. Bush, Democratic primary voters were more "change-hungry" than ever and Obama stepped into that role perfectly.

It was almost certainly the Iraq War and the various disappointments of the second Bush term that helped create such a climate for change. And Obama skillfully used this mood to mobilize a record turnout among younger liberal voters. A simple apology for her Iraq War vote plus a scathing attack on Vice President Cheney and former Defense Secretary Donald Rumsfeld for mismanaging the war would have been a better strategy than attempting to ignore this issue.

And, of course, blaming Cheney and Rumsfeld would have been exactly what the party's liberals wanted to hear. It might have helped her with independents also, as neither of these men has any support outside the most partisan Republicans.

Closely related to her underestimation of Obama was her team's failure to make a dent in her negative ratings. From 2001 through 2007, Clinton averaged a disapproval rating of more than 40 percent in the Gallup Poll. In the eight Gallup Polls of 2008, her negatives have averaged 46 percent. So she made virtually no progress in improving her image.

In fairness to her consultants, these rating have persisted for so long that it may well have been impossible to change them. But I certainly did not see much creativity on their part.

While most of her negative ratings are concentrated among non-Democrats, this drag on her popularity had a huge impact on Democrats who were desperately looking for a winner in 2008, thus pulling her below 50 percent in the primaries. I'm not usually a believer in the "personality" school of politics, but this is one case where it was probably decisive. On research trips across the South and West last fall, I found a persistent, almost irrational, dislike of her, especially among men over 40. (See "Clinton's Chances," Buffalo News, Dec. 23).

Clinton's allies surely are right when they complain that sexism played a role in her defeat. But the fact remains that she lost to a black candidate who had to overcome his own barriers of prejudice.

The tactical mistake was letting Obama take virtually all of the black vote away from her, especially black women. Blacks make up about a quarter of Democratic primary voters and are thus in a strong position to help pick a nominee if they vote as a bloc. Bill Clinton had won virtually all of the black vote against Bob Dole in 1996, and he was jokingly referred to as "America's first black president."

Until Obama picked up momentum in January, Clinton was far ahead among black Democrats. She has a three decade-long record of social concern, which should have held at least 20 percent to 30 percent of black women in her camp. But this record was not effectively communicated, and the resulting loss of 2 million black women cost her the popular vote nationally and crucial delegates in the big urban areas of the North and all across the South.

But her negative image and Obama's rally with black voters may have been beyond her control. What was eminently in her campaign's power was their ability to compete in caucuses where just a few thousand Democrats per state can make the difference. This was a clear case of a campaign staff letting its candidate down, in what California Republican consultant Bernd Schwieren called a "criminal case of incompetence." Bill Clinton himself called it "malpractice."

The organizational mistake was not preparing properly for the caucuses. On the Huffington Post Web site, Tom Edsall noted that the two candidates split the primaries almost evenly. And due to her edge in big states like New York, California, Ohio, Texas and Pennsylvania, she actually won more delegates in the primary states.

But she won only two caucus states out of 14, for a deficit of nearly 200 delegates that cost her the nomination. Texas was a classic example of this in its hybrid primary-caucus system: Clinton won the primary narrowly by 51 percent to 47 percent, to pick up an extra four delegates. But Obama romped in the Texas Caucuses that same day with 56 percent, gaining nine delegates on Clinton. So, despite her "win" in the Lone Star State, she had a net loss of delegates there.

Steve Stark wrote about her campaign's botched caucus effort on the Web site RealClear- Politics.com. "There's no excuse for this," he said. "A caucus is a simple test of organization and planning. It's like a spelling quiz in school - if you do your homework, you should pass. The Clinton campaign either never planned for the caucuses, or was so overconfident it thought Hillary would win them simply by showing up."

If Clinton had just broken even in the caucus states, her strength in the biggest states would have carried her to victory. But apparently her staff believed that they would knock out the field on Super Tuesday, Feb. 5. She did win a clear majority of primary votes that day, but Obama won almost every caucus state in February and neutralized her in the all-important delegate count.

This is remarkable considering that some of her staffers, such as Harold Ickes and Terry McAuliffe, helped write the rules on caucuses; and she started out the process as the favorite of the party regulars. So the establishment candidate lost the nomination in establishment forums designed by the Democratic Party establishment!

Every account in the political press has documented that the Clinton campaign had more than the usual intermural conflicts. Staff members should have spent less time fighting amongst themselves and more time getting Clintonites to the caucuses. More than her image problems or Obama's charismatic appeal to blacks and young voters, this organizational breakdown was the fatal blunder for Clinton.

Her career is hardly over - Clinton may yet appear on the ticket with Obama. But regardless of whether she gets the No. 2 spot, her name recognition and base among women will likely make her a strong contender in 2012 if Obama loses in the fall, or in 2016 if he wins. Numerous presidents - Adams, Jefferson, Jackson, Cleveland, Franklin Roosevelt, Nixon and Reagan - have rebounded from national defeats to win. She probably will get another chance some day.

But Clinton should learn three lessons from 2008: 1) never underestimate the difficulties of running for national office; 2) she needs to improve her image; and 3) for heaven's sake, remember to work those caucuses!