Captain reported diverting after Flight Attendant reported smoke and fumes in the cabin. The smoke and fumes were apparently associated with the Cabin Commercial Push Button on the CIDS (Cabin Intercommunication Display System) Panel.

Narrative

While at cruise altitude a flight attendant called the flight deck and stated that 'there was smoke coming from the seat area at row XX right.' I told her to see if she could determine the source of the smoke and if there was a fire for her to put it out. I was the pilot monitoring and I [requested priority handling] and asked ATC for an airport to divert to for an immediate landing. ATC recommended ZZZ and cleared us direct. I asked ATC to advise our dispatch of our intentions. I completed the QRC checklist and advised the First Officer to continue flying. I then proceeded with the QRH. I checked with the flight attendants and they told me that the smoke had stopped and there was no sign of fire. The first asked me if she should plan on an precautionary landing and I told her yes. I briefed the first flight attendant and then advised the passengers of the same. As we descended I 'all-called' the flight attendants and again asked them if there was any sign of smoke in the cabin. They said 'no sign of smoke and that the smell had dissipated.' At this point I was confident that we had eliminated the smoke source. I checked ZZZ in the manual which listed it as an alternate airport. While looking at the manual I saw that ZZZ1 is listed as a Regular airport. Per step 4 of the QRH SMOKE procedure I discussed the option of landing at ZZZ1 with the First Officer and we decided it was a better choice now that we had determined the smoke had been positively eliminated. I checked with the flight attendants again and was advised by them that the cabin was still clear of any smoke or odor. We changed our destination with ATC and I believe I sent an ACARS to dispatch advising them of the same. If not; I typed it but failed to send it. We were still very busy at that time and I do recall receiving an acknowledgement from him. I then called the flight attendants one more time and advised them that I was de-escalating the situation to a precautionary landing and we had changed our destination to ZZZ1. We landed and taxied to the gate at ZZZ1 without further incident. After arriving at the gate I advised the passengers to stay seated while the fire personnel came on board the aircraft. Fire personnel boarded the aircraft and I explained the situation to them. I asked them if they would check row XX as a safety precaution. The cabin was unlit due to the Commercial P.B. [push button] being pushed. I had turned off the Commercial P.B. while executing the QRC check list. Later that evening while reviewing the procedure I realized that the QRC directs only for the GALLEY & CAB P.B. to be turned off. Turning off the Commercial P.B was an error on my part while executing the QRC checklist. The cabin was dimly lit and I wanted to restore the cabin lights but I did not want to start the problem all over again. I asked the first if she had switched off all electrical power to the seats and entertainment system and she said yes. I believe I asked her twice and she said yes each time. I turned the Commercial P.B. back on and very quickly thereafter a flight attendant came from the back to the front and said smoke was again coming from row XX. I immediately turned the Commercial P.B. back off and told the first flight attendant to initiate emergency deplaning procedures. The passengers all exited the aircraft calmly and without incident. Fire personnel then checked row XX with thermal imaging and told me that there was no unexpected heat source. The passengers then returned for their belongings and I contacted my dispatcher and briefed him on the situation. I have attempted to be as accurate and thorough in this report as possible; however; I know there are things that I have not remembered or remembered in the wrong order.I take full responsibility for turning the Commercial P.B. off while executing the QRC. I believe the error occurred due to task saturation and an urgency on my part to rectify the situation. I also take full responsibility for turning the Commercial P.B. back on at the gate. I sincerely thought that it was a safe and good course of action to turn the lights back on. It was my decision and in retrospect I was wrong. If I am presented with a similar situation in the future it will not happen again. I do not have any suggestions to prevent this particular situation from occurring in the future. As for myself I will endeavor to be more precise and deliberate while executing an Emergency Checklist.