Manchester/Columbia: Hillary Clinton made the prospect of her being elected the first woman US president a centerpiece of her campaign, then lost a critical nominating contest to a 74-year-old man in part because women preferred him.
NBC News exit polls showed Hillary, a former secretary of state, US senator and first lady, won 44 per cent of the women's vote in Tuesday's New Hampshire primary to 55 per cent for her Democratic Party rival, US Senator Bernie Sanders.
Young women contributed significantly to Hillary's loss, and the candidate acknowledged that she struggled with young voters.
"I know I have some work to do, particularly with young people," Hillary said during a concession speech. "Even if they are not supporting me now, I support them."
With women over 45, Hillary prevailed with 56 per cent of the vote, ABC News exit polls found, but Sanders won 69 per cent among women under 45. Among women under 30, Sanders won a staggering 82 per cent.
Unlike Barack Obama, who played down his African-American roots when elected the first black president eight years ago, in this election cycle Hillary, 68, has emphasised the breakthrough a November 8 victory would represent for women.
At nearly every campaign stop in New Hampshire, Hillary or a supporter emphasised the role she could play as the first woman in the White House while Sanders galvanised young people with his promise to fix an economy he said was rigged in favour of the wealthy.
Hillary said she was trying to break the "hardest, highest glass ceiling". She campaigned alongside four women US senators, New Hampshire Governor Maggie Hassan and Lilly Ledbetter, the woman for whom an equal-pay law is named.
Former US Secretary of State Madeleine Albright reprised her line that "there is a special place in hell for women who don't help each other" while introducing Hillary at a rally on Saturday.
Hillary told a young woman the same day that she has to walk a "narrower path" because she has "got to be aware of the fact that I'm trying to be the first woman president of the United States of America, and there has never been one before, and so people don't have, you know, an image."
The remarks by Albright, the first woman to serve as secretary of state, and others by feminist icon Gloria Steinem were assailed as disparaging by young women supporters of Sanders. Steinem had said young women were drawn to Sanders because that was where the boys were.
With the next nominating contests in Nevada and South Carolina, Hillary will seek to lift her standing among women.
Katherine Wilbur, 20, a geography major at the University of South Carolina from Hopkins, South Carolina, said she had yet to decide on a candidate or party.
"I think that's ridiculous. It's 2016," Wilbur said of the suggestion that women should vote for other women. "It's not important to me."
Paige Lambert, 23, who volunteered for the Sanders campaign in New Hampshire: "I don't think I should have to vote for a woman because I am a woman."
Lambert said, "If I would have thought she'd do better, I would have voted for her. I'm not just going to vote for her because she's a woman."
Amanda Coleman, 26, of Manchester, New Hampshire, said she did not think candidates should be elected based on gender, but on their stances on the issues.