New Jersey Gov. Chris Christie has a reputation for vengeance.

And he delivered it with gusto Friday as he shocked many in the political world by endorsing GOP front-runner Donald Trump for the Republican presidential nomination.

The surprise endorsement was the first for Trump from a sitting governor - and by far his most prominent. It came as Trump rival Marco Rubio appeared on the cusp of a breakthrough following a break-out debate performance. And it marks the second time that Christie has knee-capped the Florida senator, just as he appeared to be on the rise.

At a news conference in Fort Worth, Texas, Christie described Trump as the best Republican candidate to lead the country and beat Democrat Hillary Clinton. Christie previously panned Trump as ill-suited for the office.