Vice President Joe Biden, left, telling Sen. Arlen Specter how much more fun it is to be in the majority. (AP Photo / Ron Edmonds, File)

I can't claim to have predicted Arlen Specter's defection to the Democratic Party, but I did offer my colleagues an accurate guess about what he would say in his statement: that he would be as much of a maverick in his new party as he was in his old one.

Sure enough, the statement contains this Arlenesque caveat:

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.... I will not be an automatic 60th vote for cloture.

And although I was surprised by Specter's switch, it reflects traits that have been on view throughout his public life, which I followed closely in my previous job at the Pittsburgh Post-Gazette. Notable among them is Specter's survival instinct, which long before today's party switch inclined him to, er, adjust his position to the demands of the moment.

In a 2005 column written after Specter championed a vote on some of George W,. Bush's judicial nominees, I compared the senator to the Vicar of Bray, a 16th century English clergyman who kept his pastorate as the monarchy seesawed between Protestantism and Catholicism. A poem about the vicar features this refrain:

And this is law, I will maintain
Unto my Dying Day, Sir.
That whatsoever King may reign,
I will be the Vicar of Bray, Sir.

Or the senator from Pennsylvania.