Malloy on Tuesday narrowly bested Lamont after a campaign that turned negative, with the candidates trading accusations about each other's records.
For Malloy, the primary victory was a redemption of sorts for his loss in the 2006 Democratic gubernatorial primary against New Haven Mayor John DeStefano. This time, Malloy said it was easier to differentiate himself from Lamont, a Greenwich businessman best known for challenging Sen. Joe Lieberman in 2006.
Malloy will face the winner of a three-way Republican primary.
Lamont spent more than $8.6 million in the losing effort.
Meanwhile, former wrestling executive Linda McMahon has fended off a late challenge from former Congressman Rob Simmons to win the Republican endorsement for Connecticut's U.S. Senate seat.
McMahon on Tuesday defeated both Simmons and Weston financial expert Peter Schiff in the GOP primary.
Simmons had led the race back when U.S. Sen. Chris Dodd was still planning to seek re-election. He suspended his campaign in May after losing the party's endorsement to McMahon, then restarted his efforts in recent weeks with TV ads reminding voters his name was still on the ballot.
But McMahon, who spent more than $20 million of her own money on the primary race, largely ignored his re-entry. She now faces Democratic Attorney General Richard Blumenthal in November.