“Is it nice to lock people up, put a lady in a tent without a toilet? No,” Mr. Caroll said, referring to how Ms. Hickox was treated in New Jersey after she landed at Newark Liberty International Airport on Friday. “But the alternative is, if something goes wrong, you get blamed. The decisive is what pays off.”

In Maine, Mr. LePage said in a statement that he had been trying to negotiate an agreement with Ms. Hickox, based on C.D.C. guidelines for how to prevent the spread of Ebola. Those guidelines, he said, would allow her to go about in public as long as she maintained a three-foot distance from others, and submitted to health officials to monitor her temperature and any symptoms.

Those negotiations seemed stalemated Thursday night. But Ms. Hickox, too, seemed to be stepping back from her earlier pledge to defy quarantine, emerging from her house with her boyfriend to go for a bike ride taking a trail that led them west, away from the town’s main street.

Mr. LePage said in his statement that he remained open to an agreement, but also that he would “exercise the full extent of his authority allowable by law,” and said Maine law provided the state “robust authority” to address threats to public health.

Ms. Hickox, 33, had been quarantined in a tent in a Newark hospital for four days after registering a fever of 101 on a forehead scanner at the airport Friday, though she had not registered a fever earlier in the day and has not since. She was released to Maine on Monday after her lawyers threatened legal action in discussions with the state attorney general’s office.

Thursday, the American Nursing Association issued a statement in support of Ms. Hickox, saying that she did not require quarantine under C.D.C. guidelines for monitoring by local health authorities because she had shown no symptoms. The association, which along with the American Medical Association and the American Hospital Association supports those guidelines, cautioned that overly restrictive conditions “will only raise the level of fear and misinformation that currently exists.”