NATIONWIDE — Bernie Sanders, the independent U.S. senator from Vermont, announced on Tuesday that he is throwing his hat in the ring again as he enters his second presidential campaign.

He is entering the already crowded 2020 presidential race as a Democrat again.

"Our campaign is not only about defeating Donald Trump," the 77-year-old self-described democratic socialist said in an email to supporters. "Our campaign is about transforming our country and creating a government based on the principles of economic, social, racial and environmental justice."

While running in 2016, he lost the Democratic nod to Hillary Clinton.

Sanders did not say why he was running as a Democrat, which many might find surprising considering how the party allegedly treated him in 2016.

Leaks of the Democratic National Convention's emails showed that it favorite Clinton while disparaged Sanders. That political upset sent shockwaves to the point that the DNC's chairwoman Debbie Wasserman Schultz stepped down. However, she was given a position in Clinton's campaign.

An enthusiastic progressive who embraces proposals ranging from Medicare for All to free college tuition, the question now for Sanders is whether he can stand out in a crowded field of Democratic presidential candidates who also embrace many of his policy ideas and are newer to the national political stage.

Some of the other candidates include:

The Associated Press contributed to this story.