The one constant about indoor events is the poor lighting. It’s not usually bad lighting. The people that set up the stage want the event to look good. There’s usually plenty of light from the audience’s perspective. What the camera sees is a different story.
When Hillary Clinton campaigned in Phoenix the event was held in a high school gym. I’ll wait while you finish shaking your head. So you can imagine the base lighting. Overhead lighting was the basic fluorescent tubes. The event lights were two towers holding a couple of lights each which faced the stage.
Since none of my lenses are stabilized, I also have to keep the shutter speed up to get sharp photos. Usually 1/320 is the minimum speed to keep the 70-200mm sharp. So between the low light and need for shutter speed, I was looking at ISO 3200 for decent exposure. Starting off I used ISO 1600, knowing that I’d have to bump up the exposure in Lightroom. About halfway through the event I figured I had enough safety shots. Then I decided to try out ISO 3200 to see if the images would be salvageable.