What kind of personality you need to be president

The combative and nasty nature of our political campaigns makes a lot of people wonder: "Why would anyone choose to run for office?" Only 43 men in history have been president. Looking at the people that decide to run, experts say some common themes emerge.

Much is made of the mental capacity of those vying to be the next commander in chief. But for most Americans, the idea of running for president may seem like a foreign concept.

The psychological switches that convince someone they're the most qualified candidate for the most important job are sometimes switched in hyper drive.

Becky Schamburg is a professor at NYU studying characteristics of leadership. She weighed in about the traits required: strong desire for dominance, desire to have control over others; high level of self-confidence, which sometimes manifests itself in a high level of narcissism or high level of grandiosity.

This combination of ego and ambition goes beyond just presidential runs, fueling politicians with the ability to stick it out in the face of gaffes, scandals and controversy, whether it's Clinton and Trump or Client Number 9 (Eliot Spitzer) and Carlos Danger (Anthony Weiner).

As voters weigh their options over who should become the next head of state, trying to get inside the minds of the candidates can make your head spin.