US Senator Bernie Sanders gestures during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders (Front) speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders gestures during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

A supporter attends U.S. Senator Bernie Sanders' first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders (L, rear) holds his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

Jane O'Meara Sanders, wife of U.S. Senator Bernie Sanders, speaks during Sanders' first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders gestures during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders kisses his wife during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders gestures during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

Supporters attend U.S. Senator Bernie Sanders' first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

A supporter attends U.S. Senator Bernie Sanders' first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

Supporters attend U.S. Senator Bernie Sanders' first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

A volunteer decorates a snowman prior to U.S. Senator Bernie Sanders' first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

Supporters attend U.S. Senator Bernie Sanders' first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)

U.S. Senator Bernie Sanders speaks during his first presidential campaign rally in Brooklyn College, New York, the United States, March 2, 2019. U.S. Senator Bernie Sanders kicked off his 2020 presidential campaign as a second-time runner on Saturday in his hometown borough of Brooklyn, New York, reiterating his Democratic socialist views that have been reshaping the Democratic Party. (Xinhua/Li Muzi)