[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/08/11/art.teddy0811.gi.jpg caption="Sources tell CNN that Sen. Kennedy decided to release his letter to Massachusetts Democratic leaders after word of his discussions reached the Boston Globe."]
WASHINGTON (CNN) - A source close to Ted Kennedy tells CNN that he decided to write his letter on how he believed a Senate vacancy should be filled after a series of private discussions in late June with Massachusetts colleagues and friends including Sen. John Kerry, Rep. Barney Frank and Rep. William Delahunt.
The Democratic senator wrote the letter on July 2, at a time when he was sitting down to pen a series of letters. But he decided not to send it primarily because, after consulting with Kerry and others, they concluded that it would likely disrupt already intense and tumultuous health care discussions in the Senate at that time.
Read: Kennedy's letter
"He's talking about his potential vacancy here, and the threat of Kennedy's vote on health care is a powerful incentive to get it done," said this source about the thinking at the time. "If the letter gets out, it could have a negative impact."
This Kennedy associate confirms what CNN was told by another Kennedy source - that another factor was his efforts to deal with the failing health of his sister Eunice, who died earlier this month.
The two Kennedy sources say the only reason he actually sent the letter this week was because the Boston Globe had gotten wind of some of his discussions, and were prepared to go with what Kennedy thought was an inaccurate account of his efforts - so he decided to make his desires clear by delivering the letter, knowing it would go public.
One of the sources described how "tough" this letter was for Kennedy to write, a acknowledging he will likely, and soon, no longer be in the Senate.
"It was typical of him - putting this outside himself, and thinking about health care and the state of Massachusetts," said the Kennedy source.