One more person has decided not to run for governor.
Marconi made the announcement on Thursday at the Ridgefield Community Center.
There is only another week before the state’s leading Democrats meet to choose who will get the party’s nomination for governor.
Lamont, a Greenwich businessman, beat Sen. Joe Lieberman in a primary four years ago. Lieberman then went on to run as an Independent and secured the seat.
Former Stamford Mayor Dan Malloy is also seeking the party's endorsement at the May 22 convention.
During his run for governor, Marconi made it a hallmark of his campaign for governor to push for electronic tolls on Connecticut highways as a way to help solve the state's budget deficit woes.
He said the state could reap about $1 billion a year in revenue.
He has been the Ridgefield first selectman since 1999.