told colleagues Tuesday she would be consider joining as his running mate, and advisers said she was withholding a formal departure from the race partly to use her remaining leverage to press for a spot on the ticket.
On a conference call with other New York lawmakers, Clinton, a New York senator, said she was willing to become Obama's vice presidential nominee if it would help Democrats win the White House, according to a participant who spoke on condition of anonymity because this person was not authorized to speak for Clinton.
Clinton's remarks came in response to a question from Democratic Rep. Nydia Velazquez, who said she believed the best way for Obama to win key voting blocs, including Hispanics, would be for him to choose Clinton as his running mate.
"I am open to it," Clinton replied, if it would help the party's prospects in November.
Clinton also told colleagues the delegate math was not there for her to overtake Obama, but that she wanted to take time to determine how to leave the race in a way that would best help Democrats.
"I deserve some time to get this right," she said, even as the other lawmakers forcefully argued for her to press Obama to choose her as his running mate.
Aides to the Illinois senator said he and Clinton had not spoken about the prospects of her joining the ticket.
"Certainly there'll be some plusses and minuses," said CBS News chief Washington correspondent Bob Schieffer. "The plusses are obvious. She can help him bring women to support him. She can help him with blue-collar workers. But there are some minuses, and the main minus is Bill Clinton himself. Does Obama want to bring on the questions that will be asked about his personal life?"
Obama received a steady stream of superdelegates since this morning as he approaches the magic number of 2,118. This includes several Michigan superdelegates who endorsed him today and are only awarded one half vote each.
According to the latest CBS News tally, Obama needs 6 delegates to secure the nomination. He has 2,112 to 1,910 for Clinton.
Based on expectations for tonight, the Associated Press has calculated that Obama has already effectively clinched the nomination.
Word of Clinton's vice presidential musings came as she prepared to deliver a televised address to supporters on the final night of the epic primary season. She was working out final details of the speech at her Chappaqua, N.Y., home with her husband, former President Bill Clinton, their daughter Chelsea, and close aides.
Earlier in the day, a senior Clinton campaign official confirmed to CBS News that Clinton will "acknowledge but not concede" the race tonight if Obama has secured the necessary delegates to be the nominee. The official says "she has no plans to concede the race tonight."
The Clinton campaign released a statement today saying "Senator Clinton will not concede the nomination this evening." Campaign Chairman Terry McAuliffe told CNN this morning that Obama "doesn't have the numbers today, and until someone has the numbers the race goes on."
Earlier, on NBC's "Today Show," Clinton campaign chairman Terry McAuliffe said that once Obama gets the majority of convention delegates, "I think Hillary Clinton will congratulate him and call him the nominee."
Clinton will pledge to continue to speak out on issues like health care. But for all intents and purposes, two senior officials said, her campaign is over.
Most campaign staff will be let go and will be paid through June 15, said the officials who spoke on condition of anonymity because they were not authorized to divulge her plans.
The advisers said Clinton has made a strategic decision to not formally end her campaign, giving her leverage to negotiate with Obama on various matters including a possible vice presidential nomination for her. She also wants to press him on issues he should focus on in the fall, such as health care.
Universal health care, Clinton's signature issue as first lady in the 1990s, was a point of dispute between Obama and the New York senator during their epic nomination fight.
In a formal statement, the campaign made clear the limits of how far she would go in Tuesday night's speech. "Senator Clinton will not concede the nomination," the statement said.
Clinton field hands who worked in key battlegrounds said they were told to stand down, without pay, and await instructions. Speaking not for attribution because they didn't want to jeopardize their jobs searches, many said they were peddling resumes, returning to their hometowns or seeking out former employers.
Clinton officials have said they would not contest the seating of Michigan delegates at the convention in Denver this August. The campaign was angry this past weekend when a Democratic National Committee panel awarded Obama delegates it thought Clinton deserved.