For the first time since taking office eight years ago, Mayor Michael Bloomberg is governing without the people most responsible for shaping his national image.

Trusted aides Kevin Sheekey and Ed Skyler both announced recently they were leaving the billionaire mayor for the private sector. Last week they were joined by Rohit Aggarwala, the top policy expert who created the environmental agenda that shaped Bloomberg’s reputation as an international climate change leader.

The departures mean Bloomberg will navigate his third term without some of the most important voices, personalities and expertise that have guided him throughout his entire political career.

Third terms have been historically thorny phases for New York mayors.