North Charleston, South Carolina( CNN) All eyes are on Donald Trump and Ted Cruz as Republican presidential contenders take the stage here Thursday night for one of the final debates before the Iowa caucuses.

While there has been plenty of hostility between Trump and most of his challengers, the billionaire businessman and Cruz have been on largely friendly territory for much of the campaign season. That's changed, however, as the polls in Iowa tighten ahead of the February 1 caucuses.