If he nabs the Libertarian Party line, he could hit 2-3% of the vote. As an Indie, he won't hit 1%.
His performance would largely depend on whether Cruz is cancer among moderate conservatives or not. If Cruz isn't, he's fine, but if he is, a showing of 15-30% of the vote is possible.
I want this scenario to happen both because it would make a Dem pickup possible and because I have not seen the live results of a genuine three way race (I was hoping with McMullin, but that fell through) anywhere and think it would be really cool.
Absolutely not. There is no circumstance in which Dowd gets more than 5% of the vote in this race, and I hesitate to imagine a situation where he gets over 2 or 3%. He is a nobody in terms of name id and no one in the TX GOP wants to actually give that Senate seat to the Dems, as much distaste as people have for Cruz.
Cruz
may lose in the primary to someone, but if he makes it to the general Cruz will cruise.