I don’t say this specifically about Harris, but in general, that’s wrong. The moment someone actually starts campaigning and running their polling falls. That’s because it’s easy to offer support to someone before they’re under harsh scrutiny, and you can bet Trump’s team has a ton of crap to fling at her the moment she’s the candidate. Most of it will be nonsense of course, but so is most of the crap he’s flung at everyone else.