The role of the first lady, or first man, seems often to be that you do as much as you can to "humanize" your partner. Take Lady Bird Johnson, Nancy Reagan, Doug Emhoff, Michelle Obama, etc. They tended to complement the more serious personality of their partners, Presidents of the United States. This makes sense, the President is the leader and should be seen as such, but them having somebody who is so clearly human and "sentimental" by their side allows us to relate to them.

But, I imagine it must also be incredibly difficult to be taken seriously once you have fit this persona. As Lady Bird Johnson said:

“I’ll never forgive Lyndon’s boys for turning my environmental agenda into a beautification project,” she said. “But I went ahead and talked about wildflowers so as not to scare anybody, because I knew if the people came to love wildflowers they’d have to eventually care about the land that grew ’em.”

They have a lot of sway in the public consciousness, and that even provoked Mundy to say that Lady Bird essentially acted as the Vice President for sometime after the Kennedy assissination.

It seems that they also must take on the "caretaker" role of both their husbands and the nation. Mundy writes:

...a wifely role, you could say, but is it? Someday, a first gentleman will be called upon to match that care and dedication.

Mundy points to Emhoff as the first real example of this role. He is awkward to the point that it humanizes Kamala more so than without him (think the SNL skits in the beginning of the Democratic primary races, she was depicted as a robot). But that swung sharply once people saw Doug and the rest of her family. It's curious how much of an influence this can have on us. I feel somewhat ashamed to have felt that change, but it has changed drastically in me as well from the beginning races and debates I saw her in.