There are different sorts of First Ladies as there are different sorts of Presidents.
The office is so undefined constitutionally that it varies depending on the occupant.
Jackie Kennedy raised private money to remodel the White House, and acted as supreme hostess of the nation.
Hillary Clinton piloted health care legislation.
One form of soft power that remains constant however, is that she is often a key advisor.
The power play rules of being first one 'in the room' and 'last to leave', often demanded by key advisors of their presidents, is stretched to the limit when you think of the First Lady. She is almost always the first person to see the him each morning, and the last one to speak to him before he goes to bed.
CNN pundit explains their 'theory'
Not so much with the Trump administration however.
With Melania in New York with son Baron, a power vacuum appears to have been created. And, in lieu of a formal role as First Lady, Ivanka has been made Senior Advisor to the President.
Angela Rye, a regular pundit on CNN, criticised the promotion for a member of the president's family, implying that she is 'playing at First Lady'.
Rye was responding to a point made by contributor Paris Dennard that the role of 'senior advisor' varied from administration to administration.
When we challenge these roles being ill-defined or undefined in these spaces, it means there’s nothing to hold them accountable to in terms of benchmarks. They are also hoping that this type of loose association with a job description means that they can tiptoe into conflicts of interest without any issue. We saw Ivanka doing that just last week.
I think the real challenge is she doesn’t have a real defined role because we all know what role Ivanka is playing, and that’s the role of the first lady because Melania is not checking for Donald.
The idea of a role for the 'First Family' not just the 'First Lady' was put out by the Trump Transition team in December 2016.
Not an anomaly
There have been several women who were not the spouse of the President who fulfilled the role of First Lady in the 18th and 19th centuries.
- Martha Jefferson Randolph (daughter of president Thomas Jefferson).
- Emily Donelson and Sarah Yorke-Jackson (respectively the niece and daughter-in-law of president Andrew Jackson).
- Mary Elizabeth Bliss (daughter of president Zachary Taylor)
- Mary Harrison McKee (daughter of president Benjamin Harrison)
- Rose Cleveland (sister of president Grover Cleveland)
In the UK, where there is no formal 'first lady' role, there have been times when someone who was not the prime minister's spouse carried out the role of Downing Street host.
Flora MacDonald, daughter of Labour premier and widower Ramsay MacDonald often hosted people.
So this theory is probably correct.
Problems with Ivanka's role are much more to do with the conflict of interest, and her placing alongside world leaders.
Standing in for her camera shy mother isn't much of a line of attack.