I read and watch news and politics all the time, too much. And lots of US and overseas sources. But beyond recognizing her name, I have no real clue who Martha McSally is. And I bet 99.9% of Americans probably wouldn’t even recognize her name. Not helpful to Trump, no different than McCain picking Palin.
I don’t know that being unknown is itself a problem. Palin would’ve been a great pick IMHO had she been willing/able to learn what she needed in order to fulfill her role as VP nominee. Her problem wasn’t that she was unknown, within a couple of weeks of being picked, she was as well-known as anyone. Her problem was that when she opened her mouth, things came out that subjected her to ridicule.