The fourth debate of the Republican presidential nomination race is set to take place in Tuscaloosa, Alabama, with Florida governor Ron DeSantis, former US ambassador Nikki Haley, tech entrepreneur Vivek Ramaswamy, and former New Jersey governor Chris Christie on the stage. Former President Donald Trump, the frontrunner, is absent, providing an opportunity for the other candidates to close the gap. The debate holds significance for DeSantis and Haley, who are competing for second place. Trump's decision to skip the debate and host a private fundraiser showcases his strategy to maintain his lead without engaging directly with opponents.