WASHINGTON - Hillary Rodham Clinton ended her historiccampaign for the presidency on Saturday and told supporters tounite behind rival Barack Obama, closing out a race that was asgrueling as it was groundbreaking. The former first lady, who as recently as Tuesday declaredherself the strongest candidate, gave Obama an unqualifiedendorsement and pivoted from her role as determined foe to absoluteally. "The way to continue our fight now to accomplish the goals forwhich we stand is to take our energy, our passion, our energy anddo all we can to help elect Barack Obama, the next president of theUnited States," she said in a speech before cheering supporterspacked into the ornate National Building Museum, not far from theWhite House she longed to reign in. "Today as I suspend my campaign, I congratulate him on thevictory he has won and the extraordinary campaign he has won. Iendorse him and throw my full support behind him and I ask of youto join me in working as hard for Barack Obama as you have forme," the New York senator said. With that, Clinton placed herself solidly behind her Senatecolleague from Illinois, a political sensation and the first blackto secure a presidential nomination. For Clinton and her supporters, it was a poignant moment, theend of an extraordinary run that began with an air of inevitabilityand certain victory. About 18 million people voted for her; it wasthe closest a woman has come to capturing a nomination. Joining her on stage were her husband, the former president, andtheir daughter, Chelsea, before she took their leave as sheaddressed the crowd. Obama secured the 2,118 delegates needed to clinch thenomination Tuesday after primaries in South Dakota and Montana. Heplanned to spend the weekend at home in Chicago. Clinton supporters began lining up at dawn to attend thefarewell address. A smattering of Obama backers showed up as well,saying they did so as a gesture of party unity.