Very strong rumors are circulating around Capitol Hill that Arlen Specter will switch parties and caucus with Democrats.

At least one other source is reporting it as well – Chris Cillizza over at the Washington Post…

UPDATE: Drudge reporting speculation as well.

UPDATE 2: It’s official – he has released a statement, the following is an excerpt:

When I supported the stimulus package, I knew that it would not be popular with the Republican Party. But, I saw the stimulus as necessary to lessen the risk of a far more serious recession than we are now experiencing.

Since then, I have traveled the State, talked to Republican leaders and office-holders and my supporters and I have carefully examined public opinion. It has become clear to me that the stimulus vote caused a schism which makes our differences irreconcilable. On this state of the record, I am unwilling to have my twenty-nine year Senate record judged by the Pennsylvania Republican primary electorate. I have not represented the Republican Party. I have represented the people of Pennsylvania.

I have decided to run for re-election in 2010 in the Democratic primary.

April 28, 2009

Statement by Senator Arlen Specter

I have been a Republican since 1966. I have been working extremely hard for the Party, for its candidates and for the ideals of a Republican Party whose tent is big enough to welcome diverse points of view. While I have been comfortable being a Republican, my Party has not defined who I am. I have taken each issue one at a time and have exercised independent judgment to do what I thought was best for Pennsylvania and the nation.

Since my election in 1980, as part of the Reagan Big Tent, the Republican Party has moved far to the right. Last year, more than 200,000 Republicans in Pennsylvania changed their registration to become Democrats. I now find my political philosophy more in line with Democrats than Republicans.

When I supported the stimulus package, I knew that it would not be popular with the Republican Party. But, I saw the stimulus as necessary to lessen the risk of a far more serious recession than we are now experiencing.

Since then, I have traveled the State, talked to Republican leaders and office-holders and my supporters and I have carefully examined public opinion. It has become clear to me that the stimulus vote caused a schism which makes our differences irreconcilable. On this state of the record, I am unwilling to have my twenty-nine year Senate record judged by the Pennsylvania Republican primary electorate. I have not represented the Republican Party. I have represented the people of Pennsylvania.

I have decided to run for re-election in 2010 in the Democratic primary.

I am ready, willing and anxious to take on all comers and have my candidacy for re-election determined in a general election.

I deeply regret that I will be disappointing many friends and supporters. I can understand their disappointment. I am also disappointed that so many in the Party I have worked for for more than four decades do not want me to be their candidate. It is very painful on both sides. I thank specially Senators McConnell and Cornyn for their forbearance.

I am not making this decision because there are no important and interesting opportunities outside the Senate. I take on this complicated run for re-election because I am deeply concerned about the future of our country and I believe I have a significant contribution to make on many of the key issues of the day, especially medical research. NIH funding has saved or lengthened thousands of lives, including mine, and much more needs to be done. And my seniority is very important to continue to bring important projects vital to Pennsylvania’s economy.

I am taking this action now because there are fewer than thirteen months to the 2010 Pennsylvania Primary and there is much to be done in preparation for that election. Upon request, I will return campaign contributions contributed during this cycle.

While each member of the Senate caucuses with his Party, what each of us hopes to accomplish is distinct from his party affiliation. The American people do not care which Party solves the problems confronting our nation. And no Senator, no matter how loyal he is to his Party, should or would put party loyalty above his duty to the state and nation.

My change in party affiliation does not mean that I will be a party-line voter any more for the Democrats that I have been for the Republicans.

Unlike Senator Jeffords’ switch which changed party control, I will not be an automatic 60th vote for cloture. For example, my position on Employees Free Choice (Card Check) will not change.

Whatever my party affiliation, I will continue to be guided by President Kennedy’s statement that sometimes Party asks too much. When it does, I will continue my independent voting and follow my conscience on what I think is best for Pennsylvania and America.