Kast, who has a history of defending Chile’s past military dictatorship, finished ahead in the first round of voting last month but failed to secure a majority of votes.
He was able to reverse the difference by expanding beyond his base in the capital, Santiago, and attracting voters in rural areas who don’t side with political extremes.
Kast, 55, a devout Roman Catholic and father of nine, emerged from the far right fringe after having won less than 8% of the vote in 2017.
A longtime lawmaker, he has a record of attacking Chile’s LGBTQ community and advocating more restrictive abortion laws.
If elected, he said, he will “bury” the neoliberal economic model left by Pinochet and raise taxes on the “super rich” to expand social services, fight inequality and boost protections of the environment.
In addition, the political rules could soon change because a newly elected convention is rewriting the country’s Pinochet-era constitution.