The US Census Bureau has confirmed what the state’s top political leaders were dreading: Massachusetts will be losing a Congressional seat, one of ten states in the nation to do so, according to figures the bureau released on Tuesday.

Lawmakers will turn into mapmakers next year, redrawing the state’s political boundaries to account for a smaller US House delegation, now all Democrats, that will be diminished from ten members to nine in 2012.

Parts of Dorchester and Mattapan are represented by U.S. Rep. Michael Capuano, while U.S. Rep. Stephen Lynch represents half of Dorchester, including the Columbia-Savin Hill area and the Neponset Valley. Capuano also represents Somerville, Cambridge and Chelsea, while Lynch also represents South Boston and a number of suburbs south of Boston.

Once a delegation that boasted 16 members, Massachusetts has been losing congressional seats since 1930, though it was able to hold the line at the conclusion of the last census, in 2000. The last time the state gained seats was in 1910. “It’s never a good thing when you lose a seat,” said state Rep. Marty Walsh (D-Dorchester).

The loss is based on population counts that occur every decade, overseen by the Census Bureau and used to determine the allocation of $400 billion in federal funds. While the state’s population grew to 6,559,644 residents, from 6,349,097 ten years ago, other parts of the nation, such as the south and west, grew at a faster rate. Texas picked up four Congressional seats, in part because of influx of Hispanic residents.

Mayor Thomas Menino, who has frequently sparred with the Census Bureau over the number of Bostonians they have counted, sounded a note of skepticism about the Census figures and urged Secretary of State William Galvin to review them. “I think the Secretary of State should take a very serious look at the numbers that were given by the Census Bureau, see if we can pick up numbers,” he told the Reporter.

Menino noted that the Census revised its population estimates for Boston by 10,000 people last year after his administration challenged the figures. He said the Census usually misses students and immigrants in their counts.

But state Rep. Michael Moran, a Brighton Democrat who is the state House’s top official on redistricting, said he was “pretty confident” that the numbers are accurate and the state will be losing a seat. He estimated the state would have needed an additional 175,000 people to avoid the loss.
Galvin also indicated the Census numbers were final. “This is the official count,” he told the State House News Service. “It’s disappointing.”

Avi Green, executive director of voting rights group MassVOTE, said his organization will be joining with others to create a coalition aimed at ensuring a fair and transparent redistricting process, and for lawmakers who are drawing the maps to allow time for amendments from outside groups. “Let’s take a month and have some serious public discussion because this map will be with us for ten years,” he said, adding that he is optimistic about a commitment of a fair and transparent process from Moran and the Senate’s redistricting leader, state Sen. Stanley Rosenberg (D-Amherst).

“I’ve already reached out to them and will continue to solicit their opinion,” Moran said, adding that he plans to launch a website as well as hold hearings and meetings in order to get the opinion of everybody from the “average citizen to the mayor of the city of Boston.”

Incoming state Rep. Dan Winslow, a former judge and general counsel to former Gov. Mitt Romney, told the News Service that Boston’s expected population increase, particularly among immigrant groups, could lead to the creation of a Congressional district anchored in the city and dominated by persons of color. “The Congressional districts in Boston currently fracture the minority population, which I believe is a violation of the national Voting Rights Act,” he said.

The legislative commission, likely to be headed by Moran and Rosenberg next year, won’t just be redrawing Congressional districts; they’ll be taking on state Senate and House districts as well. The redrawing of the House lines is first up, with a deadline of November 2011 for a new map to be in place.

Material from State House News Service was used in this report.