Sen. Chris 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 the late Sen. Edward Kennedy (D-Mass.) as some of the reasons why he was stepping down.

“And in the midst of all of this, I found myself in the toughest political shape in my career,— Dodd said.

Dodd said that he arrived at his decision after watching legislation pertaining to Kennedy’s signature issue — health care reform — 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 there are moments for each elected official to step aside and let others step up,— Dodd said. “This is my moment to step aside.—

In response to Dodd’s announcement, Connecticut Attorney General Richard Blumenthal (D) is expected to make an announcement this 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.

Dodd made his decision after considering his own poor standing in the polls last month, even though Dodd and his allies strongly insisted he was running for re-election until he alerted his closest confidants of his decision on Tuesday evening.

Dodd surprisingly made his decision with virtually no pressure from the White House, according to several sources familiar with his final decision.

“No, the president did not call him,— said one source close to Dodd. “In fact, the truth is that the White House has been extraordinarily cooperative and generous with Dodd.—

President Barack Obama visited Connecticut once already to raise money for Dodd, while Vice President Joseph Biden has made two trips to do fundraisers for his former Senate colleague. Dodd also has a strong relationship with White House Chief of Staff Rahm Emanuel, and top Obama adviser David Axelrod used to be his media consultant.

“They may be secretly relieved, but they’ve been great,— added the Dodd source.

John Olsen, head of the Connecticut AFL-CIO, said that Dodd phoned him Wednesday morning with the news that he was retiring.

“I believe he came to it on his own,— Olsen said. “I don’t think he was pushed.—

Olsen added that he believed Dodd also wanted the freedom to direct his attention toward reforming the economy and health care over the next few months, given his chairmanship of the Senate Banking, Housing and Urban Affairs Committee and his leading role in the health care reform effort.

“I think Dodd sees these issues left in the U.S. Senate while we still have these majorities is critical,— Olsen said. “I really think he sacrificed himself as a politician for the good of the nation, the United States Senate, and his family.—

Dodd becomes the second Senate Democrat in less than 24 hours to announce his retirement.

Sen. Byron Dorgan (D-N.D) announced Tuesday evening that he had decided not to seek another term in November. Republicans are heavily favored to pick up his open seat in GOP-leaning North Dakota.

Democratic Senatorial Campaign Committee Chairman Bob Menendez (N.J.) released a statement praising both retiring Senators. He said “their decisions to retire were heartfelt and personal and I know that they both feel strongly that their seats remain blue in November.—

Other warm wishes and tributes to Dodd’s service began flooding e-mail inboxes Wednesday.

“I know how much of an honor it has been for Chris to serve the people of Connecticut and how truly difficult this decision was for him to step away,— Senate Majority Leader Harry Reid (D-Nev.) said in a statement. “His warm personality, sense of humor and optimistic spirit has won him great respect and many friends on both sides of the aisle.—

Fellow Connecticut Sen. Joe Lieberman (ID) noted in his statement that Dodd’s retirement will bring to a close two generations of Senate service — spanning a half a century — by the Dodd family. Dodd’s father, the late Sen. Thomas Dodd (D-Conn.), served in the Senate from 1959 to 1971.

“Senator Chris Dodd will leave the Senate in January 2011 with the knowledge that he has made a difference that will last in the lives of his constituents and his country,— Lieberman said. “For that, we are all grateful.—