Senate Democratic Caucus

The Democratic Caucus of the United States Senate (sometimes referred to as the Democratic Conference) is the formal organization of all senators who are part of the Democratic Party in the United States Senate. For the makeup of the 115th Congress, the Conference additionally includes two independent senators (Bernie Sanders of Vermont and Angus King of Maine) who formally caucus with the Democrats for the purpose of committee assignments and structural organization, bringing the current total to 48 members. The central organizational front for Democrats in the Senate, its primary function is communicating the party's message to all of its members under a single banner.

Effective with the start of the 115th Congress, the conference leadership is as follows:

The conference was formally organized on March 6, 1903, electing a chair to preside over its members and a secretary to keep minutes. Until that time, this caucus was often disorganized, philosophically divided, and had neither firm written rules of governance nor a clear mission.

Since 1920, the Chair of the Senate Democratic Caucus has also concurrently served as the floor leader as part of an unspoken tradition.

After the victory of Democrats in the midterm elections of 2006 an overwhelming majority in the conference wanted to reward Chuck Schumer, then the chair of the Democratic Senatorial Campaign Committee, with a position in the leadership hierarchy. In response, then-Democratic Leader Harry Reid created the position of Vice-Chair when Democrats formally took control in 2007. Schumer ascended to Reid's position following his retirement after the 2016 elections. The position was then split, with one co-chair awarded to a centrist Senator, Mark Warner, and the other awarded to a left-wing Senator, Elizabeth Warren.

...
Wikipedia