The primary season is almost over. After Kentucky and Oregon Tuesday, the only remaining votes are in Puerto Rico June 1 and South Dakota and Montana June 3.

Jen Psaki, Obama's traveling press secretary, told The New York Times the campaign is starting to change focus, "to lay the groundwork" for the fall campaign.

Obama is expected to win Oregon Tuesday. A large majority there could give him enough pledged delegates to claim victory against Hillary Clinton, even though she is expected to win Kentucky.

By returning to Iowa -- a state, like Oregon that is almost entirely white -- Obama appears to be trying to undercut Clinton's argument that she is the stronger candidate against presumptive Republican nominee John McCain in the fall.

Obama's win in the Iowa caucuses turned him into a serious contended, one with a real chance of becoming the Democratic nominee and perhaps even the first black U.S. president, the newspaper noted.