Can you think of any time in modern history when a lower-tier candidate broke through to win the nomination? Even if you can, they didn’t have the money and media issues of today to deal with.
The only one I actually think might have some chance at traction is Huckabee, if they give him more mainstream questions at the debates. He’s really running for VP though.
What makes lower tier lower tier? It’s that we the voters are not supporting them. My point is only that many who do not support them WOULD LIKE TO but they have been convinced of their “can’t win” status. So it is a self-fulfilling prophecy. You don’t support a candidate who can’t win — and a candidate can’t win if you don’t support him.