We can't sort by votes on the new tag:
Even changing the url manually:
quietly converts the sort order to:
I agree with Sklivvz that it seems strange that the top result on the "new" tab might be very old if sorting by votes. But that didn't stop me from being unpleasantly surprised that the sort option was not available. Maybe orthogonality is overrated:
Any computer scientist who praises orthogonality should be sentenced to use an Etch-a-Sketch. —Larry Wall
It is possible to sort by votes on the popular tab for all time, but that does not seem to show all questions:
So while there is a way to sort most questions by votes, it does not seem possible to sort all questions in a tag by votes. I'm not sure which questions are excluded from the "popular" tab, however. Perhaps the solution is to remove whatever non-time-based filter is applied to popular questions when sorting by votes.