Fiorina gained far more than Cruz---but has yet to crack double digits.
In other words, the minor churning in the lower tier is meaningless.
So, no, Cruz is not going to leap from 4% to 20%.
1. Trump declared on June 16. Scott Walker declared in July 13, nearly a month after Trump declared. Scott Walker was one of the last to declare, yet he was ahead in the polls for months with double-digit poll numbers running as high as in the 20’s, so you can't claim that Trump was polling 1 to 2 % earlier because he declared late. Nor can you claim it was lack of name recognition either. Everyone knows The Donald.
2. Take your mind back to this time in 2007 if you will. John McCain was polling at around 7% give or take and seemed to be stuck there. In fact pundits had started writing him off cause he couldn't seem to get his mojo going. Giuliani was polling far ahead of him. And it went just Giuliani either. Who ended up with the nomination in 2008? You tell me.