The former first lady spoke to supporters at a victory rally in Louisville, Kentucky. She thanked them for their vote, despite what she described as pretty tough odds.

Clinton trails her Democratic rival, Senator Barack Obama, in delegates needed to secure the party nomination. She is also behind him in so-called superdelegates -- party officials and elected office-holders who are free to vote for any candidate at the party's nominating convention.

In remarks to her supporters, Clinton said the fight for the nomination is one of the closest races for a party's nomination in modern history.

Oregon is also holding a primary. Polls are still open in that northwestern state, which Obama is favored to win.

After the results are counted, Obama is expected to have a majority of the pledged delegates offered in the Democratic presidential contest.

But in a note to reporters, the Clinton campaign said any effort by Obama to declare victory after Tuesday's contests will be a "slap in the face" of Clinton supporters. More...