U.S. Senator Bernie Sanders, a self-styled democratic socialist and 2016 Democratic primary runner-up, announced Tuesday that he will run for president again in 2020.

U.S. Senator Bernie Sanders [File Photo: VCG]

"Together, you and I and our 2016 campaign began the political revolution. Now, it is time to complete that revolution and implement the vision that we fought for," Sanders said in an early-morning email to supporters.

The 77-year-old independent senator caucuses with Democrats in Congress. His progressive agenda includes Medicare for All, 15-U.S.-dollar per hour minimum wage, free college tuition, combating climate change and raising taxes on the rich.