Removed from the district are several mostly white areas, including Boston’s North End and sections of Cambridge. Randolph is about 60 percent nonwhite. The minority population in Milton, which overall is about 75 percent white, is concentrated in the three precincts added to the new Seventh District. The nonwhite population in the district will be approximately 57 percent.

Capuano, who is of Italian and Irish ancestry, said he has no problem representing a minority-majority district. “My argument is that if people voted by race or ethnicity, we wouldn’t have a Governor Patrick or a President Obama,’’ said Capuano, who called Randolph “a good Democratic town; it’s a progressive community.’’

A former Somerville mayor, Capuano was first elected to Congress in 1998, topping a 10-person Democratic field in a race for an open seat.

In every congressional race since then, Capuano has been reelected easily.

He has not faced formal opposition in the Democratic primary, and his only general election opponent was a Socialist Workers Party candidate in 2006. In 2009, he ran unsuccessfully for the US Senate in the special election to replace the late Edward M. Kennedy. At the end of 2011, Capuano had about $346,000 in his campaign treasury.

Capuano said he is happy with his new district and did not ask state legislators to change any of the lines. “I just asked them to keep all of Somerville in it,’’ he said.

The state has never had a nonwhite member of the US House. But David Harris Jr., a longtime Randolph civil rights activist and former Randolph School Committee member, said the reconfigured congressional district represents an important opportunity for a person of color to win the office in the future.

“If someone could step forward and galvanize that vote, it would be a terrific opportunity,’’ Harris said. “I don’t think it will happen this time around.’’