New Jersey governor Chris Christie is endorsing Donald Trump in the race for the Republican presidential nomination in the US.
Mr Christie said Mr Trump "will do what needs to be done to protect the American people".
The endorsement comes ahead of Super Tuesday, the biggest single-day delegate haul of the nomination contests.
Mr Christie criticised Florida senator Marco Rubio, saying: "We don't need any more of these Washington DC acts."
He memorably attacked the freshman senator at the final Republican debate before the New Hampshire primary, tripping up Mr Rubio in a moment that likely contributed to his poor performance in the state's primary.
Mr Christie accused him of parroting the same lines repeatedly and said a president should be able to think on his feet.
The endorsement from Mr Christie comes the day after Mr Rubio changed tactics in Thursday's debate and began to attack Mr Trump on a variety of fronts, from his business background to his preparedness to lead the nation.
Mr Rubio continued on Friday morning, calling Mr Trump "a con artist" during a round of morning television interviews.
Mr Trump said Mr Rubio is a "desperate guy" and added: "I don't think he's of presidential calibre."