[3] After declining to pursue a run for governor in 2018, Lembo won a third term as Comptroller by defeating Republican Kurt Miller of Seymour in a landslide victory.
Lembo opposed several of Malloy's economic development projects including a $22 million grant to Bridgewater Associates, the largest hedge fund in the world.
[11] In 2018, Lembo authored legislation forcing pharmaceutical corporations to disclose details of how they set prescription drug prices.
The effort ultimately failed when Cigna, a major insurance carrier in the state, threatened to leave Connecticut if a public option became law, as revealed by Lembo to the Hartford Courant.
Lembo was targeted by the anti-gay American Family Association in 2016 after removing them from a state-sponsored charitable giving campaign.
For his work promoting open government, he received the Bice Clemow Award from the Connecticut Council on Freedom of Information in 2013.
[21] Lembo earned the AARP Legislative Achievement Award in 2016 for his leadership of the Connecticut Retirement Security Board.
The Norwich, CT chapter of the NAACP honored Lembo with its 2019 Robertsine Duncan Memorial Award given to an individual or organization for outstanding efforts to ensure quality education for children while being an advocate on behalf of the community, city and state.