Still, in the months since the killing, Dr. Carhart has made changes at his clinic and to his lifestyle as he has openly moved to take up Dr. Tiller’s cause.

Visitors to the clinic here must pass through a metal detector, new security cameras scan outside the building and a security consultant is employed full time. Dr. Carhart says he goes out publicly only on short, unscheduled trips and rarely eats out (and when he does, he says he stays less than 30 minutes). Dr. Carhart, an Air Force veteran, said his daughter was wed this fall on a nearby military base, mainly for security and privacy.

“We do everything differently now,” he said.

Dr. Carhart declined to provide specifics on how late in a pregnancy he would be willing to perform an abortion. Dr. Tiller performed them, in some cases, as late as in the third trimester of pregnancy. Dr. Carhart’s fee schedule lists prices for abortions up to 22 weeks and 6 days (at that point, $2,100 in cash or $2,163 on a credit card), but notes that abortions after 23 weeks are available “after consultation with our doctor,” and that abortions after the 27th week may take four days.

Image The funeral of Dr. George R. Tiller in Kansas in May. Credit... Charlie Riedel/Associated Press

At his clinic in the past, Dr. Carhart said, he had performed abortions up to about 22 weeks into gestation  considered by some to be near the earliest point at which a fetus can survive outside the womb, a notion known as viability and one that is cited in many laws related to abortion.

Dr. Carhart’s opponents insist that late-term procedures violate state and federal statutes as well as professional rules. They have approached officials in Nebraska seeking an investigation. Mr. Newman, who had regularly called for investigations into Dr. Tiller’s work but strongly denounced his killing, has submitted a complaintabout Dr. Carhart to Jon Bruning, Nebraska’s attorney general. In it, Mr. Newman accuses Dr. Carhart of using improper operating procedures under shoddy conditions.

Representatives of Mr. Bruning would not comment on whether an investigation was taking place. Marla Augustine, a spokeswoman for the State Department of Health and Human Services, which regulates physicians, said Dr. Carhart had no formal disciplinary actions on his record.