Christie said he had not planned to attend the trooper's funeral even if he was in the state. He said he would have attended a groundbreaking in Essex County if he wasn't on the road with the Republican presidential front-runner.
PHOTOS: Funeral for NJ State Trooper Sean Cullen
The Republican found himself in the unflattering national political spotlight for the second time since endorsing Trump.
The cover of Tuesday's Daily News of New York showed the governor next to a headline, "Christie's Dead Cop Dis." Christie sent Lt. Gov. Kim Guadagno to the Monday funeral for Trooper Sean Cullen, who died after being struck by a driver as he responded to a car fire. Meanwhile, Christie campaigned with Trump in Florida and North Carolina.
Christie ordered flags to half-staff in New Jersey and in a statement Friday called Cullen a "loving and devoted father, son and brother whose memory will live in in this hearts of his family."
Chris Burgos, the head of the state troopers' union, which has fought bitterly with Christie in court over public pensions, was sharply critical of the governor.
"We did not expect someone who has consistently shown disdain for law enforcement to pay his respects to the Cullen and State Police family," Burgos said.
Christie has missed three funerals for officers from the state who died in accidents since December. He attended the funeral for a state trooper who died in June, right before he launched his campaign.
PHOTOS: Loved ones honor NJ state trooper at vigil
On the campaign trail, the governor got swept up in Trump's attacks on fellow candidate Ohio Gov. John Kasich, who he criticized for spending time out of state. Trump said Kasich spent more time in New Hampshire than Christie ahead of that state's primary.
"I hated to do that, but I had to make my point," Trump said.
Christie was also pictured at a rain-dampened air hangar in Ohio next to Trump, who was holding an umbrella over himself.
On Super Tuesday, Christie was widely mocked online for his blank stare while standing behind Trump during a news conference. He later said he wasn't being held hostage, as some speculated, and that's just what standing behind someone looks like. He recently dismissed the attention.
Christie has said he's backing Trump because he has the best chance of beating Democratic front-runner Hillary Clinton in November's general election. Christie has seen his ratings at home fall further in polling since the endorsement.
"I think that what we see here is a guy - the governor - really attempting to ingratiate himself with Donald Trump doing everything he can including taking a political hit in his home state, but still he's getting wet, outside the umbrella," said Montclair State University political science professor Brigid Harrison.
On Tuesday, an editorial in the Star-Ledger, one of the nine New Jersey papers that have called for Christie's resignation, demanded the governor repay the state for the cost of his state security detail while traveling on behalf of Trump. Also Tuesday, Jersey City Mayor Steven Fulop - an expected 2017 gubernatorial candidate - launched a website calling on Christie to step down.
Christie said recently he wouldn't resign and that newspapers were just trying to find ways to stay relevant by printing scathing editorials. He also said that he would refocus on New Jersey.
"I'm going to do my job," Christie said. "The people of New Jersey will see it and react to it, and I'll do better."