Seems the Vermont senator found his earlier comments a bit too harsh. From Halperin:

Any clear-eyed appraisal of the campaign at this stage adds up to two conclusions:

The bottom line is that, first, Senator Obama continues to hold a lead that appears to be insurmountable, and recent indications are that more and more unpledged delegates have begun to add their support to his column.

And second, John McCain, who has been making one mistake after another, is getting a free ride on those gaffes, because the Democratic candidates have to focus not on him but on each other.

Senator Casey’s endorsement of Senator Obama in Pennsylvania is the latest sign of how the race is going.

A Democratic victory in November is important to the future and to the change in course that the American people want and deserve. The last thing the American people need is for Senator McCain to continue a third term for President Bush.

Senator Clinton has every right, but not a very good reason, to remain a candidate for as long as she wants to. As far as the delegate count and the interests of a Democratic victory in November go, there is not a very good reason for drawing this out. But as I have said before, that is a decision that only she can make.

Senator Clinton has begun a tremendous career in the Senate, and she has a bright future ahead of her. She faces difficult decisions ahead, and I wish her the best.

In other words, says Leahy, stay in, but you're going to lose.