The President of the Massachusetts Senate is the presiding officer. In the United States Congress, the Vice President of the United States is the ex officio President of the United States Senate. In Massachusetts, however, the President of the Senate is elected from and by the Senators. The President, therefore, typically comes from the majority party, and the President is then the de facto leader of that party.
The current President of the Massachusetts Senate is Stan Rosenberg, a Democrat. Democrats have had a majority in the Senate since 1959.
A = American, D = Democratic, R = Republican, W = Whig