Sen. Christopher J. Dodd (D-Conn.) announced Wednesday that he will not seek a sixth term this November, bringing to a close a political career that spanned more than 30 years in Congress. Dodd’s departure is a boost for Senate Democrats, who have long viewed him as the most vulnerable incumbent up for re-election in 2010.

In his announcement, Dodd acknowledged that he was aware of his political standing in his home state, but said it was a combination of factors that led him to announce his retirement at the age of 66. Dodd cited the death of his sister, his recent battle with prostate cancer, his two young daughters and the death of his dear friend and colleague late Sen. Ted Kennedy (D-Mass.) as some of the reasons why he was stepping down.

“And in the mist of all of this, found myself in the toughest political shape in my career,” Dodd said.

Dodd said that he arrived at this decision after watching legislation on Kennedy’s signature issues — health care — pass the Senate on Christmas Eve, followed by a trip to the late Senator’s grave site at Arlington National Cemetery that day.

“And that is how I came to the conclusion that, in the long sweep of American history, there are moments for each elected public servant to step aside and let someone else step up,” Dodd said. “This is my moment to step aside.”

Connecticut Attorney General Richard Blumenthal (D) is expected to make an announcement Wednesday afternoon that he will run for Dodd’s seat. Blumenthal is the most popular Democrat in the Nutmeg State after holding his office for almost two decades, and his Senate bid significantly increases Democrats’ likelihood of keeping the seat.