Clinton and Obama are still set to face off in several more primaries, including Kentucky and Oregon on Tuesday, but Obama has been increasingly portraying himself as the nominee already facing Republican. Obama has scheduled appearances later this week in Iowa and Florida as he looks ahead to swing states in the general election.
"You can declare yourself anything, but if you don't have the votes, it doesn't matter," Clinton said Monday in a satellite interview with an Oregon television station before a campaign appearance in Kentucky.
Clinton has "changed her tone" after days of sounding more conciliatory towards Obama, reported CBS News correspondent Jim Axelrod. Now, he said, Clinton is "back to pressing her case hard."
The former first lady trails Obama in the delegate count by such a margin that it is mathematically unlikely for her to overtake him in the remaining primaries, which end June 3 with Montana and South Dakota.
In a memo Monday morning, Clinton Communications Director Howard Wolfson wrote that if Obama declares himself the Democratic nominee Tuesday night, as Politico suggested in a report, it will be "a slap in the face to the millions of voters in the remaining primary states and to Senator Clinton's 17 million supporters." (Politico now reports that Obama will not declare victory Tuesday.)
"Premature victory laps and false declarations of victory are unwarranted," Wolfson wrote. "Declaring mission accomplished does not make it so."
Both candidates have been angling to win over the party leaders and elected officials known as superdelegates, whose support will likely determine the nominee. Obama recently surpassed Clinton in committed superdelegates.
Clinton has also tried to make the case that if the results of disputed primaries in Michigan and Florida are included, she would lead Obama narrowly in the overall popular vote. Clinton won both contests, but the results were voided because they took place in January in violation of Democratic Party rules. Obama and three other Democrats, but not Clinton, removed their names from the Michigan ballot after all the Democratic candidates agreed not to campaign there or in Florida.
Since then, Clinton has argued that both states' delegations should be seated at the Democratic convention in August. The DNC rules committee has a May 31 meeting to consider options.
"Once we include Florida and Michigan, neither Senator Obama nor I will have enough delegates to get the nomination, so there is no way that this is going to end anytime soon, because we're going to keep fighting for the nomination," Clinton told voters in Prestonburg, Ky.
To bolster her popular vote argument, Clinton's campaign has concentrated this week on Kentucky, where she's leading in polls, in order to run up her vote there. On Friday, the New York senator left Oregon, where she trails Obama, to campaign exclusively in Kentucky.
Clinton has also been arguing to superdelegates that she is more tested and experienced and has a better chance of beating McCain.
She said Monday that she is the "more progressive candidate" and dismissed Obama's large crowds, like the record rally of an estimated 65,000 in Portland on Sunday. Clinton said Obama, who has refused to debate her since they faced off before the Pennsylvania primary last month, would "rather just talk to giant crowds than have questions asked."
Speaking to several hundred people in a high school gymnasium later, Clinton renewed her campaign's argument that Obama's victories in states with caucuses instead of primaries are somehow less significant because turnout was lower.
Clinton also revived her pitch that many states where he has beaten her, like Alaska, Idaho and Utah, matter less because they would not be competitive for Democrats in November.
"So I'm going to make my case and I'm going to make it until we have a nominee, but we're not going to have one today and we're not going to have one tomorrow and we're not going to have one the next day," Clinton said. "And if Kentucky turns out tomorrow, I will be closer to that nomination because of you."
Later in Prestonburg, Clinton added an unusual rationale for her candidacy - an analysis by President Bush's former political adviser Karl Rove that she would be tougher for McCain to defeat.
"Just today I found some curious support for that position when one of the TV networks released an analysis done by - of all people - Karl Rove, saying that I was the stronger candidate," she said.