It seems like now you need either a fairly extensive political background for pundits to discuss or an eye-catching campaign like Trump's in 2016.
Trump had the advantage of being very well-known. Pretty much everyone in America knew who he was.
I don't think extensive political backgrounds are enough. Plenty of Senators and Governors get stuck in the low single digits.
One question is whether you pretty much need to be as well-known as Elizabeth Warren (to pick a high-profile Senator) to have a chance in a presidential primary.