Pete Buttigieg, the 37-year-old mayor of South Bend, Indiana, is on the older cusp of the millennial generation.

But almost 20 years ago, he caught on to one millennial trend way before the rest of his cohort.

As a senior in high school, Buttigieg won the John F. Kennedy Profile in Courage Essay Contest for a piece he wrote praising Bernie Sanders, then a congressional representative. He called the Vermont socialist an "outstanding and inspiring example" of authenticity and idealism in politics.

"Sanders' positions on many difficult issues are commendable, but his real impact has been as a reaction to the cynical climate which threatens the effectiveness of the democratic system," Buttigieg wrote.

Fast-forward two decades, and the two men are competing against each other in the Democratic presidential primary.

The difference between Buttigieg and his 77-year-old opponent?

"A somewhat different message and a very different messenger," Buttigieg said.

Elected mayor of his hometown at 29, Buttigieg has for years drawn national attention as a rising star in the Democratic Party from an unexpected ZIP code. President Barack Obama mentioned him on ashortlist of promising young Democrats in 2016.

Buttigieg told INSIDER in a March phone interview that as the lone millennial voice in the 2020 field, he hopes to reframe the policy debate around values and make pragmatic the new progressive.