HI David,
I think the PMP gives a ton of tools that can be utilized in a leadership role to improve your capabilities, but i wouldn't say that is the primary focus of the certification. Thinks like effective problem resolution and communication are definitely things that will prove beneficial to any leader, as well as things such as risk management. But leadership, in its totality, is a very versatile study which incorporates a variety or practices and principles that can vary based on the industry and company culture.
I would say obtaining a PMP would not hurt your cause in any way shape or form, but secondary degrees like an MBA could give you a lot more focus on topics primarily related to leadership in a corporate capacity. Hope this helps and good luck on your journey.