Has America already had a female president?

In a year's time, as the US presidential election nears its climax, it's possible Hillary Clinton will be the Democratic Party's candidate, with a chance of becoming the first female president. But there was once another woman in the White House who came close to fulfilling this description - Eleanor Roosevelt, wife of America's wartime president Franklin Delano Roosevelt.

The Washington press corps became very excited in June 1996 when it emerged that Hillary Clinton had been having imaginary conversations with Eleanor Roosevelt. Reporters portrayed these motivational chats as supernatural seances. Even her husband, Bill Clinton, joked recently that his wife used to "commune" with this previous Democratic first lady who'd died in 1962.

Hillary Clinton has always been at pains to explain in her various memoirs that she was simply looking for comfort from a woman who "inspired and fortified" her. She'd kept a portrait of Eleanor Roosevelt in her office in the White House and her conversations were just "a useful mental exercise to help analyse problems". As often as not, Hillary wrote, Eleanor's spirit would respond "by telling me to buck up or at least to grow skin as thick as a rhinoceros."

No surprise, then, that when Clinton launched her presidential campaign with a rally on Roosevelt Island in New York's East River, it was interpreted as a hat-tip to her heroine, as much as it was to FDR.

Eleanor is famous for saying that she would "rather be chloroformed than run for office", but she was a consummate political operator in her own right. She was also a wronged wife, which may help to explain her significance for Clinton.

Eleanor was still a shy teenager when she met Franklin, her distant cousin. He was good-looking and ambitious and they married in 1905, when she was 20. Some years later, two events in quick succession altered their relationship.

First, was the upsetting discovery in 1918 that Franklin Roosevelt had become romantically attached to Eleanor's own social secretary, Lucy Mercer. Eleanor had found a secret stash of love letters when she was unpacking her husband's trunk on his return from a tour of Europe as Assistant Secretary of the Navy. "It's a twofold stab in the heart," says the historian, Prof Allida Black. "First of all, it's her husband. Second of all, it's her closest associate. She feels bereft in both camps."

The second episode was possibly even more traumatic. In 1921, at the age of 39, Franklin Roosevelt was struck by a polio attack, which left him paralysed from the waist down. To begin with, it seemed as if his ambition for high office would have to be cast aside. FDR's own mother, Sara Roosevelt, wanted her son to retreat to the family home at Hyde Park in New York state and forget about his political dreams. But Eleanor argued with her formidable mother-in-law and insisted his hope of entering the White House should be kept alive.

The combined effect of these shocks meant that the Roosevelt marriage evolved from an intimate union into something more like a political partnership. As well as tending to her wheelchair-user husband and campaigning on his behalf, Eleanor also pursued her own interests. In the 1920s, she spent much of her time championing issues such as world peace, better conditions in the workplace and women's rights.

When FDR ran for the presidency in 1932 and won, Eleanor was "filled by the greatest possible sense of dread" says Allida Black. Her uncle, Teddy Roosevelt, had been president, so, as Black puts it, "she knows the White House eats women". As it turned out, though, her role went far beyond hosting tea parties in the Rose Garden.

Due to her husband's disability, she ended up doing a lot of the exhausting travel that would otherwise have fallen to him. This became particularly important as the New Deal took shape - with its numerous programmes designed to pull America out of the Great Depression. Eleanor would often be on the road, crisscrossing the country and visiting New Deal projects to assess which ones worked and which fell short.

She also instituted her own White House press conferences for women journalists and from 1935 onwards, she was writing her own syndicated newspaper column called My Day.

"It was a bit like a blog," says Maurine Beasley, one of Eleanor Roosevelt's biographers. "It was laughed at by professional journalists but it had a tremendous readership because it appealed to ordinary people with a very conversational style."

Eleanor became the first president's wife to testify before a congressional committee, and the first to address a national party convention. She was also an influential behind-the-scenes adviser to FDR, just as Hillary Clinton was an adviser to Bill Clinton six decades later, when she helped produce the ill-fated healthcare reforms, sometimes known as Hillarycare.

"FDR knew that she had incredible talents and intellectual gifts and he relied on her perspective," says Bob Clark from the Roosevelt Presidential Library. "He didn't always necessarily follow her advice… but she could bring people and issues to him in a more direct manner than his other advisers could do."

Being unelected meant that Eleanor could do things her husband could never dream of. The story goes that in 1938, when she was invited to speak at a welfare conference in Birmingham, Alabama, she refused to sit in the white-only section of the hall. After being told that she couldn't sit in the black section, she took her chair and defiantly sat in the middle instead.

Sometimes there was a tension between her idealism and her husband's pragmatism. The two clashed, for example, over the decision to intern thousands of Japanese-Americans after Japan's bombing of Pearl Harbor in 1941. Eleanor had made known her deep misgivings.

"He asked her not to openly challenge him on this and as a First Lady in wartime, she felt compelled to follow that request," says Bob Clark. "But she also then led by example. She visited the camps. She talked about the loyalty of Japanese-Americans in her My Day column. So while she wasn't openly criticising the President's policy, she was openly expressing support for the people who were interned in those camps."

After FDR's death in 1945, just months into an unprecedented fourth term in office, Eleanor Roosevelt left the White House a widow. Allida Black believes that if she had stood as a candidate for the US Senate herself, she would have been elected in a landslide. "But she didn't want to run for public office, because she didn't want to spoil the opportunities for her sons to have political careers. They were eager to follow in their father's footsteps."

Instead, Eleanor Roosevelt ended up with an unexpected career as a diplomat.

She was the only woman on the first American delegation to the UN and she chaired the committee which drafted the Universal Declaration of Human Rights. Written in 1948 in the aftermath of World War Two, it enshrined the rights and freedoms which should belong to every citizen on the planet, and it remains a model for constitutions around the world. When Hillary Clinton launched her campaign on Roosevelt Island, the UN building was visible in the background - again, a subtle tribute to her heroine perhaps.

Over the next year, if her campaign gathers momentum and sees off the strengthening challenge from Democratic rival Bernie Sanders, Hillary Clinton may well continue channelling the Roosevelts.

It's one way she can try to fend off criticism of the Clinton family's immense wealth. The Roosevelts, after all, were affluent and privileged but that did not stop FDR carrying out reforms that benefited ordinary people.

If, on the other hand, the Clinton bid begins to implode in the coming months, then Eleanor's advice to female politicians may well become more relevant than ever before: "Every woman in public life needs to develop skin as tough as rhinoceros hide."

Listen to Naomi Grimley's documentary on Eleanor Roosevelt on the BBC World Service. Click here for transmission times or to listen via the BBC iPlayer.