"Within reach," Obama says in Des Moines, after Oregon win, Kentucky thumping.

WASHINGTON Sen. Barack Obama staked a claim to the Democratic presidential nomination on Tuesday, sweeping Oregon but getting trounced by Sen. Hillary Clinton in Kentucky, exposing problems he might face in winning middle-class white votes in the fall campaign.

Obama traveled to Iowa, the swing state that handed him his first victory crucial to establishing his viability to mark at an outdoor rally in Des Moines the milestone of having won the majority of pledged delegates. He said he is within reach of the nomination, though he is short of the 2,026 delegates needed to clinch.

With party unity vital to Obama if he is to beat GOP presumptive nominee Sen. John McCain, Obama praised Clinton.

We have had our disagreements during this campaign, but we all admire her courage and her commitment and her perseverance and no matter how this primary ends, Sen. Clinton has shattered myths and broken barriers and changed the America in which my daughters and yours will come of age.

The Obama campaign emphasized his winning the majority of all the elected delegates Tuesday night as part of his drive for the support of the remaining superdelegates public officials and elected officials Obama needs to win.

With his wife, Michelle, and two daughters with him, Obama talked about his presidential journey.

Change is coming to America, Iowa, Obama said. . . . Thats what Ive seen here in Iowa. Thats what is happening in America our journey may be long, our work will be great, but we know in our hearts we are ready for change, we are ready to come together, and in this election, we are ready to believe again.

While the long primary campaign is winding down, Clinton campaign spokesman Howard Wolfson said Obama was declaring a premature victory, as Clinton pledged to keep on going through June 3, the last of the nominating contests.

By the time this historic Democratic primary contest is concluded, voters in all 50 states and the territories will have chosen either the first African American or first female to be a viable contender.

Clinton celebrated her big Kentucky landslide, 65 percent for her to 30 percent for Obama, in Louisville.

In Oregon, where Obama wound up his campaign with a massive rally of 75,000, he was beating Clinton 58 percent to 42 percent.

With votes still to be cast in Montana, South Dakota and Puerto Rico and the Democratic National Committee grappling with what to do with the disputed delegates from Michigan and Florida punished because the states voted early, against party rules Clinton said, Thats why I am going to keep making our case until we have a nominee, whoever she may be.

Obama needs only about 100 more delegates to secure the nomination based on the existing rules. Clintons only prayer is convincing the DNC rules and bylaws committee meeting at the end of the month to seat the Michigan and Florida delegates according to a formula that favors her. Even if she prevails, Obama is far enough ahead that he may win even without Florida.

Obamas win in the Iowa caucus vote in a nearly all-white state was important because it demonstrated his broad appeal to whites and convinced skeptical blacks that the nation was ready to accept the biracial Obama. But race did become a factor in the more recent contests.

Kentucky exit polls showed seven in 10 whites voted for Clinton. Only one-third of Clinton backers said they would vote for Obama, with another 40 percent defecting to McCain and the rest saying they would stay home.