A Quinnipiac University survey released Tuesday found Cruz essentially deadlocked with longtime poll-leader Trump in Iowa: Trump stood at 25 percent and Cruz at 23 percent, within the margin of error. That’s more than double Cruz’s standing in the Oct. 22 Quinnipiac poll and it follows a Sunday survey, released by CBS and YouGov, that also placed Cruz in second place in Iowa, at 21 percent, trailing Trump but beating previous Iowa leader Ben Carson.
Looks like Cruz will win Iowa, scores well in South Carolina and carry the momentum to Super Tuesday particularly in southern states (Alabama, Arkansas, Texas, Georgia, Oklahoma, Tennessee, etc)
He has favourable calendar at least till April (Blue states New England Primaries)
You've essentially answered your own question. Cruz has surged just in time to be a formidable opponent to current-frontrunner Trump. His support has steadily increased, particularly in light of good debate performances. I would give him around a 50% chance of winning the Iowa caucus right now, if not a higher chance. Not sure if he will eventually win the nomination, but he will certainly be a top contender for it.
