The anti-conservative establishment has obvious reasons for running the ads for Rubio, and Huck has a paycheck to defend.
I don’t think an Iowa win is that significant for a conservative like Cruz, though he certainly has to do well.
The Media already declared Cruz the winner in Iowa. I even heard Carl Rove say it.
If Cruz doesn’t win, he’s done. If Trump wins, he will be unstoppable.
It’s also possible that someone polling in the single digits will have a late surge and win. It happened 4 years ago.