There's only one Clinton now. She's been great

Hillary Clinton's memoirs end in 2001, just after she was elected to the Senate and eight years before she became Barack Obama's Secretary of State. They're called Living History, but her own political career was still in the future when the Clintons left the White House for the last time. The woman who stepped down as the US's chief diplomat two days ago is living proof that Scott Fitzgerald was wrong when he said there are no second acts in American lives.

It's hard to believe there won't be a second volume of Clinton's memoirs. The original book finishes on a sentimental note as she recalls the outgoing president "taking me in his arms as we waltzed together down the long hall" of the White House, but she's older and savvier these days. She's completed this phase of her career looking weary – she's travelled almost a million miles and visited 112 countries – but also much more comfortable with herself; the time when she seemed to change her hairstyle by the week is long gone. So is the ambitious lawyer who put her husband's political career before her own and entered the White House as First Lady, a role which mostly frustrated her attempts to modernise it.

The change in Hillary Clinton's fortunes since those days is nothing short of astonishing. During Bill Clinton's first presidential campaign, she ended up fielding lurid allegations about his infidelities. During his second term as President, she dismissed claims about his affair with Monica Lewinsky as part of a "vast right-ring conspiracy" until it became clear that they had more to do with his habitual sexual incontinence. It seemed little short of tragic to hear this smart woman resorting to clichés, averring that she always knew Bill Clinton would be "a hard dog to keep on the porch".

These days, it's her husband who needs the qualifying first name when we say "Clinton". Hillary is going strong at 65, while the former president, just a year older, works the international conference circuit and plays golf. Obama's verdict that she "will go down as one of the finest secretaries of state we've had" may be generous, given her reluctance to break ties with old allies such as Hosni Mubarak, as the Arab Spring unfolded. But she's been outspoken, urging China to respect human rights, and she's put equality for gay people at the heart of US diplomacy.

Clinton leaves office with sky-high approval ratings. One of her lesser-known achievements is the creation of an Ambassador-at-Large for Global Women's Issues, to ensure gender is considered in foreign policy decisions. While a recent health scare may have put another run at the Democratic nomination in doubt, the fact that people are talking about a 69-year-old woman as a possible candidate in 2016 shows how much she has changed public attitudes. Any woman who has lived in the shadow of a powerful man should look at Hillary Clinton and recognise the transformative power of a challenging job.

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