The shock endorsement came after Rubio, in an abrupt shift cheered by anxious Republicans nationwide, shattered months of relative peace with Trump in Thursday night's GOP debate.
Mr Trump was ahead in polls in 10 of the 11 states set to vote on "Super Tuesday" next week.
"I had a special relationship with Governor Christie because he had helped me so much in my race", Hogan said.
Trump says Rubio is a "desperate guy" and said, "I don't think he's of presidential caliber".
"There is no one who is better prepared to provide America with the strong leadership that it needs both at home and around the world than Donald Trump", said the New Jersey governor, speaking alongside the real estate mogul in Fort Worth, Texas.
"Like Trump, Chris Christie is a pathetic, corrupt man with a tiny ego", former Jeb Bush communications director Tim Miller tweeted. Christie said he intends to serve his full term, then go into the private sector.
Donald Trump, left, and Chris Christie talk together following the CNN Republican presidential debate at the Venetian Hotel & Casino on Tuesday, Dec. 15, 2015, in Las Vegas.
Rubio, who has admittedly struggled with his own personal finances such as student loans, accused Trump of withholding his tax records because they likely show "he's not as rich as he claims to be".
Christie's unexpected endorsement interrupted the news cycle just as Trump's biggest remaining challenger, Florida Senator Marco Rubio, was building up a head of steam. After which Rubio continued to read several of Trump's tweets pointing out spelling mistakes in the Tweets. "What we are dealing with is a con artist", Rubio told a crowd of about 2,000 in Dallas.