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Chris Christie vigorously defended his endorsement of Donald Trump Thursday and insisted his much-ridiculed facial expressions during Trump's press conference earlier this week did not betray regret or panic about his choice.

"No, I was not being held hostage," he said told reporters during a press conference in New Jersey. "No, I was not sitting up there thinking 'Oh my God, what have I done?'"

"I wasn't upset, I wasn't angry, I wasn't despondent," he said. "I wasn't anything other than happy that we had done as well as we had done that night, and listening to someone giving a press conference in front of the national press corps. "

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A sometimes befuddled-looking stare on Christie's face during Trump's lengthy Super Tuesday night event led to ridicule of the New Jersey governor on social media.

On Thursday, Christie fiercely stood by his backing of Trump's candidacy, arguing that the real estate mogul is the best remaining GOP candidate to defeat Hillary Clinton in November.

But he declined to take personal aim at Mitt Romney, who eviscerated Trump earlier Thursday as a "fraud" and a "phony" who would be dangerous for the party and for the world.

"Mitt Romney's a very good friend of mine" he said of Romney, who won his endorsement during the 2012 presidential contest. "We have a political disagreement."

Christie dismissed criticism from several newspapers in the state - including the Star-Ledger - about the time he has spent out of state during both his presidential run and his efforts to support Trump.

And the former presidential candidate also said he has urged Trump not to leave the Republican Party despite the tensions between the GOP's establishment wing and the insurgent streak that supports the real estate mogul.

"I have urged him not to leave the party," Christie said of Trump. "I will not answer any question beyond that."