Rep. John Olver (D), who has represented Massachusetts for 10 terms in the House, will retire at the end of his current term.

"Last December, I announced that I intended to seek to continue my congressional service beyond 2012," Olver said in a statement announcing his retirement. "Over the past six months, circumstances within my family have substantially changed, and I now find I must reconsider my earlier decision."

Olver has said previously that his wife, Rose, is battling cancer.

Olver, 75, first came to the House in 1991 in a special election, following the death of longtime Rep. Silvio Conte (R-Mass.). One of the most liberal members of the House, Olver won his 2010 reelection race by 25 points over Republican William Gunn.

"My friend and longtime colleague John Olver is a quiet man who lets his large accomplishments speak for him," said Sen. John KerryJohn Forbes KerryJohn Kerry to NYU Abu Dhabi: We can't address world problems by 'going it alone' Juan Williams: Trump's dangerous lies on Iran Pompeo: US tried, failed to achieve side deal with European allies MORE (D-Mass.) in a statement. "He’s a public servant of principle who has served western Massachusetts with great skill and deep passions belied by his unassuming and humble demeanor."

Although known for his shyness and reluctance to put himself in the spotlight, Olver and four of his Democratic colleagues were arrested at the Sudanese Embassy in 2006 for protesting violence in Darfur.

Olver's retirement could make it easier for the state's all-Democratic House delegation as they work to eliminate one district from the state's congressional map. Massachusetts is losing one seat in the House in the once-per-decade redistricting process.

Under the current map, Olver's district includes most of western Massachusetts and is geographically the largest district in the state.

—This story was updated at 5:30 p.m.