Without even checking, I know that Trump was polling at between 1 and 3% just 3 months ago(that is around 1st of June), and was far far behind Walker who was leading all the national polls. The Iowa Caucus is not for another over 5 months to go. You can't assume that today's poll numbers for Ted Cruz or anyone else will be the same come Jenuary. Trump's own poll trajectory should tell you that. What we do know is that Ted Cruz has a solid organisation in all the states that count, strong grass roots support as confirmed by the fact that he has raised more from more people than anyone else on the Republican side(175,000 people contributed in the last quarter alone). He has the organisation and the money to fight for as long as it takes.
All true, but huge differences. First, Walker led a national poll or two, but very few state polls (IA for example). But Trump has steadily risen in EVERY national poll and almost every state poll (he trails favorite sons Kasich in OH and Walker in WI). So he’s up, and up big, in NH, IA, SC, NV, NC, TX, GA, AZ, FL, AL, and W VA. Now, that is just amazing, and his lead in all of these has been steady or rising. So, no, Ted isn’t going to come back. He may win a couple of delegates to barter away, but only if Trump needs them after Super Tues.