First Ladies: America’s secret weapons
It's one of America's toughest political gigs, a "full-time, all consuming job" that is unpaid and unelected but with the eyes of the world actually upon you.
As the 2020 campaign heats up towards the November election, the stark differences between the current holder of the office of First Lady of the United States and the woman who would replace her are becoming increasingly clear.
Former model Melania Trump, 50, is the most reserved and mysterious First Lady for more than half a century, according to writer and historian Carl Sferrazza Anthony.
Having served eight years as Second Lady while her husband Joe Biden was vice president to Barack Obama, Dr Jill Biden, 69, has a proven record as a public figure, campaigner and in her own right as a professor of literature.
"They couldn't be more different," says Anthony, who is a board member of the National First Ladies' Library and is currently writing a biography of Jackie Kennedy's early years.
Compared with her outgoing predecessors including Michelle Obama, Hillary Clinton, Barbara and Laura Bush, Mrs Trump is something of an enigma.
She rarely gives interviews, is usually pictured only with her husband and has worked on few of the "pet projects" that other First Ladies have championed.
"She has a public profile that is perhaps the lowest and the most abstract of all," Anthony says.
To find a comparison: "You would have to go back some 70 years to Harry Truman's wife Bess Truman, who really was uncomfortable being a public figure and really did not grant any interviews and had very little interaction with both the general public and the media."
Should Dr Biden step into the role, she would be "a return to a more traditional" holder of the position.
"Any person who has spent eight years being Second Lady is at the greatest possible advantage," he says. "Once they hit the White House, they are ready to go."
Another difference between these two women, typically described in campaigns as "secret weapons" is how much they have and will feature on the election trail.
"Despite the truncated nature of the 2020 Democratic primaries, we did see Jill Biden take on a very much a physical presence outside of her husband," Anthony says.
"She did many events on her own but she is also very familiar and comfortable discussing policy and what her husband's stand has been on various issues.
"That's something else that Melania Trump has not done at all, whereas Jill Biden will get out on the stand and just take random press questions on controversial issues without any screening of what those questions might be from the media."
The role of First Lady is traditionally one of the country's most revered, but also one of the more challenging.
Ronald Reagan noted in 1982: "You know, with the First Lady the government gets an employee free; they have her just about as busy as they have me."
There is also the constant scrutiny and attacks from their spouse's opponents.
So it's not surprising that both Mrs Trump and Dr Biden have had moments where they weren't so keen on the position.
For Melania Trump, that meant waiting five months to join her newly-elected husband in the White House after he was inaugurated.
Instead, she spent the first half of 2017 at the couple's New York base, ostensibly so their then 11-year-old son Barron could finish his school year before she took up the unfamiliar role.
According to a new biography, the Slovenian-born model who became Trump's third wife after a five-year courtship in 2005, also used these months to renegotiate the couple's pre-nuptial agreement.
Pulitzer Prize winning author Mary Jordan wrote that Melania needed to "cool off" after the 2016 campaign brought widespread allegations of her husband's infidelities.
In The Art of Her Deal Jordan said Melania knew how much her newly elected husband needed her and used the first months of 2017 "to amend her financial arrangement with Trump - what Melania referred to as 'taking care of Barron'."
But despite wide supposition that the Trump's marriage was an unhappy one and that Mrs Trump didn't want her husband to run for president, Jordan wrote that the pair loved each other and she supported him.
"There is ample evidence that from the very beginning (that) Melania not only accepted and embraced Trump's political aspirations but was also an encouraging partner," she wrote.
"They are both fighters and survivors and prize loyalty over almost all else."
In Jill Biden's case, the reluctance to be First Lady came when she felt her husband wasn't ready to run for president several times over his decades-long political career.
According to writer Jonathan Van Meter, in 2004 Dr Biden was so incensed by repeated urgings for Mr Biden to run that she interrupted a meeting with Democratic strategists at their Delaware beach house wearing a bikini with the word "no" written on her stomach.
Later, she was concerned that Biden in 2016 hadn't recovered enough from the loss of his son Beau, to cancer, the year before.
But this time around, Van Meter says he has no doubt she was ready.
"I'm kind of surprised in a way, because there are those stories about her not wanting to run in the past," Van Meter says.
"I guess it was a surprise that she was so gun-ho about it this time. But I get the sense that she really is ready."
A contributing editor to New York magazine and Vogue who has written about many celebrities and politicians, Van Meter has profiled Jill Biden twice in 13 years and admits he's a "huge fan".
"Of all of the people in politics that I've ever interviewed, she's without question my favourite one. She's the most authentic, the most hilariously funny. She laughs constantly," he says.
"What's amazing to me is how she managed to maintain all her soul and her personality through all of these years of being married to Joe, being married to the senator and then him running for office so many times.
"I often say people would vote for Joe just because of Jill, because she is unlike every other person and is true to herself."
While the two women contrast on many points, one area in which they are similar is in their influence on their husbands and their political careers.
Melania Trump was instrumental in the choice of Vice President Mike Pence in 2016, having vetted him and his wife over a weekend away together.
And Jill Biden has said she will play a part in her husband's choice of running mate, set to be announced in coming weeks.
While Biden has pledged to choose a female VP candidate, Jill is reportedly vetting the top names and has appeared at fundraisers in recent months with some of them.
"I would hope he would listen to me and get my advice, but it has to be his decision," Jill Biden said last week.
Karen O'Connor, a political-science professor at American University, says Biden will also be considering how much she can work with the spouse of the eventual Vice President candidate.
"If I was (Jill Biden), knowing that for the next four years my job is going to be tied up not only with my husband, but also with the spouse of the Vice President, it's got to be entering the equation," O'Connor says.
Originally published as First Ladies: America's secret weapons