Saquib A. Siddiqui & Muhammad Jawad found that Emotional Intelligence is significantly predictive of managerial effectiveness. All four factors - Self-awareness, Self-management, Social awareness, and Relationship management - were positively related to managerial effectiveness.
I would say a big five questionere, focussing on openess, agreeableness and neuroticism if your looking for personality traits. However it really depends on the vision/mission of the company. Maybe the specific tasks of that role will help you to determine competence?
In addition to the personality and intelligence tests, especially taking into account the good experience in work teams and the management of human talent.
Besides the fact that i don't totally agree with your answer i have a question for you. This is not to start a discussion about who is right or nature vs. nurture, I am just curious.
You say leaders are born. However you refer to "leadership skills". Are skills not learnable by defenition? I am looking forward for your vision about this topic.
You may need to look at the person's track record in addition to others things to consider if that person is fit to contest for such leadership position.
I can't see through the mind of the Question-asker but I will say using psychological test at the final stage by the team of Examiners will not be a bad idea. Apart from competency test using certification and experience, there is a need to examine the person considering for such post for social and metal stability using the method mentioned.