Back and Fill is nothing but to act indecisively; to change one's direction repeatedly; to reverse one's course. (Originally nautical, referring to alternately filling the sails with wind and releasing the wind.)
The president spent most of his speech backing and filling on the question of taxation.
This measure will never be passed if the town meeting continues to back and fill.
The other candidate was backing and filling on every issue, depending on whom she was addressing.