Michelle Obama’s popularity exceeds her husband’s — and last night’s speech gave us one glimpse into why that might be. She delivered an amazing, passionate endorsement of why we should re-elect her husband. (She even convinced me, a die-hard Democrat feeling unenthusiastic about the president.) The speech is already being referred to as one for the ages.

Just as interesting to me was how she completed the transformation of what we think of when we think of a First Lady — and more than that, women in power. Remember 2008 — the blue V-neck dress with three-quarter-length sleeves? Then there was the red-and-black misstep on Election Night. Since then, there have been dozens — hundreds — of mostly beautiful outfits (faithfully chronicled at Mrs-O).

As many others have noted, Mrs. Obama’s clothes are often chosen to reflect a theme or show a particular allegiance. She’s skilled at choosing designers whose backgrounds relate to the event at hand (a designer with roots in the country of a visiting head of state, for instance).

So it’s reasonable to consider her outfit last night and what it signifies. (You can see lots of great images here.) The dress is patriotic — it contained both red and blue in it. But it was quietly patriotic rather than being in-your-face, like the red suits we used to see on Nancy Reagan. (Ann Romney seemed to look both forward and backward in her choice of outfit for her speech at the RNC — a dress, not a suit, but in the classic red. The next night she wore a blue suit. Safe choices.)

Moreover, it obviously wasn’t a suit. Mrs. Obama is rarely seen wearing a suit (in fact, I’m having trouble thinking of when she has worn one). She’s done more than anyone else recently to do away with the idea that a powerful woman needs to wear a suit.

On the contrary, this was a dress — very feminine, with its full skirt and pretty pattern. (The pink, which Mrs. Obama has worn before, shows that completed the outfit just emphasized this.) And this dress, by African-America designer Tracy Reese, showcased her assets beautifully — her height, her sculpted, famous arms. (By contrast, the 2008 dress did none of this — it covered up her arms and made her look hippy rather than gorgeously curvy.)

I worked with a lovely client recently and we talked about the 1980s style of wearing scarves — with blouses and suits in a way that made them look like lady-ties and created a women’s version of classic male work attire. For many women today, that was a long time ago. But as Lily Ledbetter’s appearance at the convention last night shows, women’s equality in the workplace is far from being a dead issue.

In fact, feminism, broadly defined, is arguably at the center of this election. Mrs. Obama is of course well aware of the stakes for women in this election. In her own way, she’s shown us that what we wear is not superficial, it shows who we are — in her case, a strong, smart woman who telegraphs the very modern conviction and traditionally feminine need not detract at all from her effectiveness in the world of electoral politics, that most elevated discourse of power.

(Read more good analysis at the Root, and keep an eye on Mrs. O for more about this dress.)

Ketura Persellin is an image consultant, writer, and public speaker in Washington, DC.