Mr Trump said he “might even get to like [Mr Christie] again” following his “very truthful statement” about Ms Haley.

The former president’s political action committee said in a statement that he had “already vanquished eight challengers before a single vote has been cast because Republican voters want a strong leader who will reboot our economy, secure our border, make America energy independent again, and keep our families safe”.

This was Mr Christie’s second unsuccessful bid for the Republican nomination – he lost to Mr Trump in 2016.

Mr Christie had hoped to act as an attack dog for a field of Trump rivals who dared not cross the Republican base, which remains deeply loyal to the former president.

The strategy resulted in some zingers during the primary debates, but without Mr Trump on stage, Mr Christie failed to land any direct blows.