"The days of the 'Great Man' theory of leadership--where one sole leader rules over the masses from their ivory tower--are long gone," Rebecca Newton, a business psychologist and visiting fellow in the department of management at the London School of Economics and Political Science, writes in Harvard Business Review.

Studies have found that co-leadership can positively contribute to closer bonds between team members, increased collaboration, and more innovative ideas, but if two leaders cannot get along, all those benefits go down the drain. 

Newton experienced the upside and downside firsthand. After designing and facilitating "the first collaborative training" program between police departments and two polities whom had a history of conflict, she and her colleagues identified five keys to successful co-leadership.

Agree to Agree.

When bringing two leaders from quarreling parties together, Newton says it is critical to not only focus on "putting the past aside," but to prioritize "a joint, peaceful future." A baseline mutual commitment is essential from the start.

Share the goal, divide the role.

Newton says two leaders must share ownership of the company's overall goal, but the roles and responsibilities should be divided. "Explore and understand each other's strengths and expertise, then go through a detailed process of agreeing who is responsible for what," she writes. According to a study on co-leadership by O'Toole, Galbraith and Lawler, two leaders are more effective when they make distinctions on who is in charge of what. "This isn't a one-off conversation. Make co-leadership sustainable by regularly re-evaluating your roles and effectiveness," Newton writes.

If you're confused, so is everyone else.

If a shared leadership role is unclear to you, you better believe your partner and every employee is also going to be confused. "We tend to focus on how we navigate this relationship for ourselves, but it can be equally tricky for others to navigate 'us,'" Newton writes. "Be mindful of your joint impact on others." You need to be clear about the roles and distinctions you both share with the team and ask for regular feedback from employees--both an individual leader, and as a duo.

Be first to share praise and first to accept blame.

Co-leadership can't devolve into a popularity contest; you both share responsibilities for success and failure. The worst thing you can do is start taking individual praise for something you both did, then shift blame to the other leader when things go poorly. 

Perpetually reevaluate roles.

As you both evolve in your respective roles,  talk about how responsibilities should also evolve. "[There are] endless ways both you and your co-leader may want to change the dynamic of your relationship. Be open to these changes in your partner, and share your own evolving goals," she writes.

You have the greatest impact on your co-leader.

If you don't treat your co-leader like a leader, things will unravel quickly. As co-leader, it is your responsibility to positively impact the other leader's experience--and vice versa. "Honest conversations exploring the reality of this impact--what's great, what's challenging, and what feels limiting or restrictive--may be emotional and very likely will be uncomfortable, but will be worth it," she writes.