Hillary Rodham Clinton was taking the stage Tuesday in a role she would rather not play - telling her loyal delegates at the Democratic National Convention that they need to line up behind Barack Obama, the man who dashed her hopes of becoming America's first female president. Clinton's appearance was the main event of the convention's second night, but it was far from the role she envisioned more than a year ago when she launched her presidential bid. She was the prohibitive front-runner then but soon found herself in a riveting struggle with Obama that she could not win. Obama, seeking to become the first black US president, needs Clinton supporters, especially the white, working-class voters who were some of her strongest backers. They hold the key to must-win swing states if Obama is to win the White House. Clinton has urged them to vote for Obama.