Longtime Democratic Representative Edward Markey coasted to victory late Wednesday in a special election to fill the Massachusetts senate seat vacated by former senator John Kerry.
Markey, 66, will fill the unexpired term of Kerry, who resigned in February to become US secretary of state.
Markey beat his rival, 44 year-old Republican former Navy Seal Gabriel Gomez, in the heavily Democratic state by ten percentage points, according to official returns compiled by local media.
However the six-year seat is up for grabs again in November 2014, and Markey could be facing a stiff challenge from popular Republican former senator Scott Brown.
In 2010 Brown stunned observers when he won the senate seat of the late Edward Kennedy, delivering a key vote to opponents of Democrat Barack Obama. Brown however lost the seat to Elizabeth Warren in the 2012 election.
The outcome of the Wednesday vote maintains the 54-46 majority the Democrats have in the US senate, a majority that includes two independents who usually vote with Democrats.
Massachusetts Governor Deval Patrick had appointed his former chief of staff, William "Mo" Cowan, to temporarily fill Kerry's seat until the election.