Basically, the New Hampshire Union Leader endorsed Chris Christie for President, just before the New Hampshire primary that ended Christie's Presidential career. Which isn't a big deal, in and of itself; a person's suitability for office does not necessarily reflect his ability to be ahead in the polls, as even a cursory examination of Donald Trump's current political arc might show. But it was Christie's later endorsement of Donald Trump that grated on the Union Leader:
Watching Christie kiss the Donald’s ring this weekend — and make excuses for the man Christie himself had said was unfit for the presidency — demonstrated how wrong we were. Rather than standing up to the bully, Christie bent his knee. In doing so, he rejected the very principles of his campaign that attracted our support.
If you were wondering whether Chris Christie had any political future, stop wondering. Between this and the fact that the Union Leader insists that Christie told the paper that he'd never endorse Donald Trump in the primary, this cloud will follow him around for the rest of his political life*. Which is a shame; I enthusiastically supported him myself when he ran for governor of New Jersey. I'm sorry that he's sunk this low, but he chose his own path.
*Ironically, the only real political path forward for him at this point would be a Cabinet post in a not-Trump administration. I say 'not-Trump' because if Trump gets the nomination, well. Hillary Clinton is simply not going to tap a Republican governor to be her next Attorney General. Even one from a blue state.