By Tara McKelvey

One woman, Nikki Haley, held a position with a cabinet-level rank as ambassador to the United Nations, but she resigned last autumn.

“It’s kind of a double-edged sword,” says Heidi Hartmann, president of a non-profit organisation, the Institute for Women’s Policy Research in Washington.

“It really is hard for these women to walk the right line – they are seen as either too strong or not strong enough. I think there’s implicit bias.”

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