New Jersey Governor Chris Christie has endorsed Donald Trump in his bid to become the presidential nominee for the Republican Party. 

Gov. Christie was a candidate himself, before dropping out of the race after a poor showing in New Hampshire earlier this month, and surprised many by choosing to back Trump on Friday. 

The two went head to head on a number of issues during the campaign, with Christie insinuating that Trump was someone who didn't care about the laws as he was "used to being able to fire people indiscriminately on television" and strongly criticised his proposed ban on Muslim travel to the United States. 

Speaking about Trump in December on the Face the Nation program, Christie also stated that "what you need is a president who’s had the experience and the know how to do this, and not someone who’s just going to talk off the top of their head". 

However, changing his mind on Friday, Christie stated that "I am proud to be here to endorse Donald Trump for president of the United States. The best person to beat Hillary Clinton on that stage last night is undoubtedly Donald Trump". 

The endorsement comes after a difficult debate for Trump against Senator Marco Rubio and Senator Ted Cruz, in which Rubio impressed and put the billionaire on the back foot. 

Rubio followed that up with a number of insults on the campaign trail on Friday morning, but Christie brushed off those attacks as the "flailing punches in the final days of the campaign". 

Trump stated that while he's "not big on endorsements, this was an endorsement that really meant a lot".