DeSantis' decision leaves only former United Nations Ambassador Nikki Haley as a serious challenger to Trump ahead of the critical New Hampshire primary.
Ahead of the general elections in November
DeSantis, seen by Republicans as the most promising alternative to Trump, dropped out of the race shortly after his defeat to Trump in Iowa.
With DeSantis' departure, former President Trump, who still enjoys support among Republican voters despite facing four criminal investigations, and Haley are neck and neck in the race.
But DeSantis' supporters are more likely to back Trump than the more moderate Haley. Andrew Smith, director of the University of New Hampshire Research Center, said about two-thirds of DeSantis supporters in New Hampshire cited Trump as their second choice.
Trump, who has spent much of the past year attacking DeSantis, praised the governor at a rally in New Hampshire on Sunday evening and said he looked forward to working together to defeat President Joe Biden, the likely Democratic nominee.
According to polls, Trump has a double-digit lead over Haley in New Hampshire. On February 24, he also leads in the South Carolina primary. A loss for Haley in South Carolina, where she served as governor from 2011 to 2017, would be a major blow to her nomination hopes.