Who is Colombia's new president?

Who is Gustavo Petro, Colombia's first leftist president? He’s a [deep breath] sixty-two-year-old-ex-leftist-guerilla-turned-mayor-turned-opposition-leader who rode a wave of voter anger to a narrow victory over a populist construction magnate last June. Got that?

But according to Petro himself, the answer is much more simple. “I’m a fighter,” Petro told Ian Bremmer in this episode of GZERO World. “I’ve been a fighter all my life in a country that has been through very difficult moments."

He was swept to power by a slim margin in June thanks mainly to young Colombians, after promising them something different in a country that's been rocked by mass protests over inequality and corruption.

Petro, who started his political career as a leftist guerrilla in the 1990s, wants to fight climate change by ending oil exploration and to massively increase social spending by taxing the rich more.

But whether he’ll be able to follow through on his promises is another question entirely.

Watch the GZERO World episode: Gustavo Petro: the guerilla-turned-president who wants to "develop capitalism"