The story

Veteran Pennsylvania Sen. Arlen Specter switched from the Republican to the Democratic Party on Tuesday, saying he has found himself increasingly "at odds with the Republican philosophy."

"This is a painful decision. I know I'm disappointing many of my colleagues," he said at a news conference announcing the move. "The disappointment runs in both directions.

"I'm putting principle at the top of the list," he added. Read full article »

CNN's Ed Hornick and Deirdre Walsh contributed to this report.

All About Arlen Specter • U.S. Senate