The Democrat made the announcement on Friday, saying it was a "tough decision" but he feels it's best for the state and the Democratic Party to rally behind a single candidate. He says "now is the time where we all have to work together. We have to be cohesive."
He is throwing his support to Greenwich businessman Ned Lamont, who ran for governor in 2010 and for the U.S. Senate in 2006. He is urging other candidates to follow suit.
Harris is a former mayor of West Hartford, a state senator and a former chairman of the Connecticut Democratic Party.
Democrats are meeting at their May 18-19 convention to choose candidates for the November elections, including governor.