Ya, I think he was speaking about keeping up public support for the mission until it is achieved. McCain is there for the duration until achieved, no matter what the body count. That's my take.
My take as well, but statement's like that just can not be made in the Middle East and it deserves approbation.
He's saying, if the U.S. casualties continue, that public support will not and our presence will not.
What message do you think that sends the remaining insurgents?