on (someone's) part
1. As far as is related to, regards, or concerns someone; to the degree that someone is involved or a part (of something). On the employees' part, the company's merger means that many will be losing their jobs. Jane on her part has been instrumental in getting this project off the ground.
2. As comes from or is done by someone. Guarantees on the banks' part must be provided to assure the country's citizens that their money is safe during this period of recovery. There has been no shortage of effort on his part to make sure this campaign has been successful.