Democratic Party Chairman Howard Dean and the Democratic congressional leadership released a statement urging the party to rally behind Obama, and several lawmakers, including Iowa Sen. Tom Harkin, Colorado Sen. Ken Salazar and Louisiana Sen. Mary Landrieu, all endorsed their Illinois colleague.
Obama also announced he had named a three-person vice presidential vetting team that included Caroline Kennedy, daughter of the late President Kennedy.
On the telephone call with impatient congressional supporters that included New York Rep. Charles Rangel, a longtime political patron, Clinton was urged to draw a close to the contentious campaign, or at least express support for Obama. Her decision to acquiesce caught many in the campaign by surprise and left the campaign scrambling to finalize the logistics and specifics behind her campaign departure.
It was an inauspicious end for a candidacy that appeared all but indestructible when it began Jan. 20, 2007.
Armed with celebrity, a prodigious fundraising network, a battle-tested campaign team and husband who also was a popular two-term former president, Clinton was believed by many observers to be unbeatable.
But in Obama, the New York senator faced an opponent who appeared perfectly suited to the time - a charismatic newcomer who had opposed the Iraq war from the beginning - in contrast to her - and who offered voters a compelling message of change. Clinton voted for the legislation that authorized military force against Iraq, a decision that hampered her campaign from the beginning.
After a disastrous showing in the leadoff Iowa caucuses on Jan. 3, Clinton won New Hampshire's primary Jan. 8, setting off the state-by-state war of attrition with Obama that followed.
Her fortunes rose and fell like a fever chart: She was up in Nevada, down in South Carolina. Then, after a roughly even finish on Super Tuesday Feb. 5, she suffered a string of unanswered losses that, almost before Clinton noticed, put Obama so far ahead in the delegate hunt that all the big-state victories she piled up couldn't close the delegate gap.
By March, her options limited, Clinton adopted the persona of a tenacious fighter for the middle class. She powered successfully through primaries in states like Ohio, Pennsylvania, Indiana, West Virginia and Kentucky, showing grit that earned her valuable political currency.
White men, blue-collar workers, socially conservative Democrats and older women were especially receptive to her message, and her strong showing with those voters exposed Obama's vulnerabilities among those groups.
Democrats whose No. 1 concern had been ending the Iraq war at the campaign's outset started worrying more about the economy. That was a switch from Obama's strength to hers.