Obama, D-Ill., won Oregon by 16 points, swamping Clinton among male white voters. But Clinton, D-N.Y., won Kentucky by a wider 35-point margin. She has now won five of the last seven primaries.

Nevertheless, the Oregon victory propelled Obama to a decisive lead over Clinton in the number of elected delegates to the Democratic National Convention in Denver this August.

The flow of superdelegates to Obama continued. He is now within 100 delegates of a decisive overall majority of convention delegates at Denver to seal his presidential nomination, and Clinton cannot catch him.

Abraham Lincoln famously said he would like to have God on his side but he had to have Kentucky. Obama appears confident of divine support, but to win the nomination he doesn't need the Blue Grass State. Winning the presidency without it is, however, another story. For that, he probably will need Clinton on the ticket as his running mate to consolidate the Democratic base.

The long, bruising contest for the Democratic presidential nomination has exposed the strengths and weaknesses of both its main contenders. Obama has run an intellectually brilliant, superlatively organized campaign with a masterly manipulation and wooing of the U.S. national media. He out-organized and out-generaled Clinton in most of the caucuses and in most of the minor states. He out-thought her, out-charmed her and out-maneuvered her.

Given all the advantages in name recognition, grassroots support and funding Clinton enjoyed at the outset, she deserved to lose. Her choice in campaign strategists and state campaign chiefs was unremittingly dire. She showed a repeated pattern of favoritism and sexism -- picking underqualified women as opposed to qualified men or women. One of her main arguments, that she had vastly more experience of national government and administration than Obama, was exposed as empty, even farcical.

But Clinton exposed Obama's underlying weakness, too -- a weakness rooted not in race or gender but in perceived class.

Obama, despite his humble origins, was widely perceived as an elitist, and Clinton made the most of that. For all her stumbles and bungles, she was able to deny Obama a primary win in the major states of California, New York, Texas, Florida, Michigan, Pennsylvania and Arizona. It is unprecedented in modern U.S. political history that a presidential candidate for either major party without the advantages of incumbency in the White House could lose all those primary contests and still confidently look forward to claiming his party's presidential nomination.

That is why, although Clinton could not win the race herself, she showed sufficient strength to make the case that Obama cannot win without her.

Obama was also exposed as having a thin skin and a glass jaw. His strategy of being positive and rising above negative campaigning paid off brilliantly for him. But it was also essential because, as his bruising clashes with Clinton in the six-week Pennsylvania primary contest revealed, he remained extremely sensitive to criticism and remained very vulnerable when pinned down by unscripted, unanticipated aggressive questioning. He also showed a repeated pattern of opening his mouth and making elitist-sounding comments that outraged significant groups of voters.

If this was a routine, "business as usual" election with things generally going well for the American people, Obama would be a deer caught in the headlights of the Republican Party's attack machine like previous unsuccessful Democratic presidential nominees George McGovern, Jimmy Carter, Michael Dukakis, Al Gore and John Kerry before him.

Obama is certainly a vastly more inexperienced and potentially vulnerable candidate than Carter, Gore or Kerry. He is not a decorated war hero or war veteran like McGovern and Kerry, and he has had zero executive experience in government, unlike governors Carter of Georgia, Dukakis of Massachusetts and Bill Clinton of Arkansas. Clinton carries longstanding negative perceptions and baggage with her, too.

But this is not a "business as usual" year. The continued war in Iraq, unprecedented soaring global and U.S. oil prices and alarming, rising food prices all testify to the failure of the Bush administration's most important policies. For all Obama's political weaknesses, victory in the national presidential campaign remains within his grasp. If he can bring Clinton on the ticket or win her full support, he can carry a united Democratic Party with him into the fall campaign.