She settled on “really awful.”

Those close to Mr. Christie said he had anticipated the furor of his endorsement, but had been a bit taken aback by the depth of the vitriol over the past few days. In his mind, linking arms with Mr. Trump was practical, loyal and politically savvy, in keeping with his decision, in 2011, to become the first major Republican official to endorse Mitt Romney, who ultimately became the nominee.

Privately, they said, Mr. Christie and his team attribute the anger to the feeling of helplessness that once-powerful Republican leaders feel over Mr. Trump’s ascent, something those leaders did little to stop and now want to pin, perhaps unfairly, on the governor.

“I went into this with my eyes wide open; I knew it would make some people upset,” Mr. Christie said during his monthly radio show on Monday.

Hinting at his frustration with Republicans who have second-guessed him but stayed out of the campaign, he added: “I’m not an on-the-sidelines guy. I’m not going to be one of these people who sits on the side and snipes.”

But Mr. Christie’s enthusiasm for politics means traveling out of state, an expensive habit many expected the governor to curtail after he quit the presidential campaign a few weeks ago.

According to The Star Ledger of New Jersey, Mr. Christie has spent all or part of 520 days outside the state since the beginning of 2013. The trips, collectively, cost hundreds of thousands of dollars in flights, meals and lodging for the governor’s 24-hour security detail, which is typically four to six people, Ms. Weinberg said.

All of it, she said, is footed by New Jersey taxpayers.

“He’s costing us a heck of a lot of money,” Ms. Weinberg said.