Perhaps it was appropriate that Carrol Frazier Landrum was sitting in his Toyota Camry several weeks back when he decided to make his public fight with the state of Mississippi official.

With a local news camera rolling, Landrum dialed the state and calmly, if defiantly, left a voice mail.

“I’m Dr. Landrum,” he said, sitting in the driver’s seat, one hand gripping the steering wheel. “I called to tell you that I have chosen to not resign my medical license.”

Before hanging up, the 88-year-old World War II veteran added courteously: “I thank you kindly.”

As The Washington Post reported earlier this month, that same Camry is the source of an ongoing dispute between Landrum and the Mississippi State Board of Medical Licensure, which has asked the octogenarian doctor to turn over the medical license he’s carried since the Eisenhower administration.

His offense, according to the state: running a mobile clinic out of the car, which the doctor turned to after gang violence forced him out of the apartment complex where he had been working in tiny Edwards, Miss..

Surrendering to the board’s demands would be an ignominious end to Landrum’s proud career, which stretches back more than 55 years in small towns and rural communities throughout poverty-stricken Mississippi, where the doctor treated low-income patients, often at no charge.

Landrum — who told The Post he grew up poor and sympathized with the plight of the underprivileged — said he doesn’t seek out patients, but tends to those who call upon him when they have nowhere else to turn, even when they can’t pay. It is, he said, his duty, laid out in the Hippocratic Oath that he’s spent a lifetime upholding.

“If you’re going down a highway and somebody is hurt in a car accident, you stop and attend to them,” he said. “And if you’re in a shopping center and somebody is having a heart attack, you stop and help. It’s your duty as a physician, and this is no different.”

Two weeks after The Post’s story on Landrum was published, some things have changed while others have not. The doctor is still under investigation by the board and remains nervous about his future.

“I’m still worried,” he told The Post this week. “I’m still concerned about what might happen, but I have a little more confidence that I might get to keep my license. That’s what I hope, anyway.”

Landrum’s confidence has grown because of the outpouring of support he’s received since his story garnered widespread attention. An online petition states that Landrum is treating “poor or disabled people who aren’t able to travel to seek medical attention and would not receive treatment otherwise.”

To date, the petition been signed by nearly 50,000 people around the world. There was a period in mid-January, Landrum said, when his phone rang every 15 minutes with another supporter offering encouragement. Landrum said somebody soon plans to deliver a second petition to the state board, this one signed by about 1,500 locals, including the mayor of Vicksburg, Miss.

In his home town of Edwards, and in surrounding communities like Jackson and Clinton, the support has been nearly overwhelming, Landrum told The Post. The doctor said he is stopped multiple times each day — in restaurants, at gas stations, while idling at traffic lights — by locals who want to say “thank you” and encourage him to continue working.

“I was at a gas station today, and this man came up to me and said he works with disabled people and was happy that I’m doing the work I’m doing,” Landrum said. “He just shook my hand and was just real pleased. It meant a lot.”

Even more humbling, Landrum said, is that a new office is being built for him in a building that was already under construction. Once it’s finished, he said, he plans to move in immediately, to get back to work in a professional setting.

“A whole bunch of people — churches, local individuals and one contractor — have swooped in and are going to get it all done in short order,” he said. “It’ll have two treatment rooms, an office space and a waiting room. I’m just thrilled.”

Landrum said he hasn’t heard from the board since Andrew Pitts, a state investigator, told him to surrender his license or face the public humiliation and damaged reputation that could come from appearing in front of the board.

Fox News reported this week that it was unable to find any law or regulation barring doctors from operating out of their vehicles, and the Mississippi Board of Medical Licensure confirmed to Fox that there have been no disciplinary actions against Landrum. A list of recent disciplinary actions makes no mention of the doctor.

The state board’s executive director, H. Vann Craig, again declined to confirm for The Post that an investigation has begun. During a brief telephone conversation this week, Craig said: “I have no comment. Do not call me back.”

According to Fox News, Pitts confirmed that an investigation is underway, but declined further comment.

As petitions supporting Landrum add more and more signatures, people in and around Edwards have continued to show support for the doctor.

“He’s doing a great service here, really, a great service,” Dan Mashburn told NBC affiliate WLBT. “Because these people can’t afford to go to doctors.”

“Dr. Landrum was my doctor when I was like 7 years old,” Ruth Daniels told the station. “He has taken care of all my nine sisters and brothers.”

Landrum told The Post the support he’s received has not only inspired him to continue fighting to keep his license, but also to become a better public health servant.

“If they have that much confidence in me, I just want to go all out and do my best for them,” he said. “I will continue to see patients when they desire to be seen, to make the correct diagnosis and to prescribe the correct medication and try and keep their expenses down as much as possible.”