Zohran Mamdani promised Thursday to show left-wing politics can succeed as he took over as New York mayor for a term sure to see him cross swords with U.S. President Donald Trump.

Thousands of people gathered in freezing conditions in the United States’ largest city to celebrate the 34-year-old Democrat’s inauguration after his impressive political rise from relative anonymity just a year ago.

“They want to know if the left can govern. They want to know if the struggles that afflict them can be solved,” Mamdani said outside City Hall.