Obama said on Tuesday night that he had gained the Democratic nomination after winning the most pledged delegates during a gruelling five-month series of primary polls.
 
And hours later Democrats sent a strong signal in a conference with Clinton that it was time for her to bow out, The Associated Press reported.
 
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Clinton is to urge Democrats to focus on the general election in November and defeating John McCain, the presumptive Republican candidate.
 
A campaign official said Clinton and her advisers had discussed various ways of ending her candidacy, including suspending it so she could retain control of her delegates to promote healthcare issues.
 
The other options include freeing her delegates to back Obama and ending her candidacy unconditionally, the official said, adding that Clinton had not yet made a decision on which option to take.
 
On Tuesday, Clinton reportedly said she remains open to the idea of being Obama's running mate.
 
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Five months of voting concluded on Tuesday night with primaries in Montana, won by Obama, and South Dakota, won by Clinton.
 
Obama's campaign had urged the last 150 or so undecided superdelegates  - senior Democratic officials - to make their endorsements before the voting ended.
 
Many did so throughout the day to give Obama the 2,118 delegates he needed to defeat Clinton.