Joseph Kennedy III, the grandnephew of assassinated president John F. Kennedy, ran a campaign for a US Senate seat which he eventually lost.
His defeat marked the first time the storied American political dynasty lost a state election in the state.
Joe Kennedy’s opponent Ed Markey is a political veteran who built an image as the fiery liberal in the race.
Harnessing the state’s progressive energy, Ed Markey successfully beat out the primary challenger of the Massachusetts Primary.
The 39-year-old Kennedy said he called Markey "to congratulate him and to pledge my support" in the months ahead.
With votes still being counted, Markey was leading around 55 percent to 44 percent.
The race pitted two well-liked progressives against each another, but it was Markey's organizational energy and appeal to the ascendant left that won out over Kennedy.
"Tonight is more than just a celebration of an election, it is a celebration of a movement," Markey wrote on Twitter.