There is no reason to expand the number of Hillsborough County commissioners from seven to nine, much less have the entire board be elected from single-member districts. Board chairman Sandy Murman did the right thing in withdrawing her proposal. This is a change that would only benefit politicians, not taxpayers or the cause of good government.Murman said Hillsborough’s population of 1.4 million makes it too hard for the seven-member board to serve its constituents. She said expanding the board and having all members elected in single-member districts would bring local government closer to the people.But the existing system is fine. Commissioners have aides and a huge professional staff to help them serve constituents. And the current arrangement — where four members are elected in single-member districts, with the other three elected countywide — means that all voters have the chance to elect a majority on the board. Having countywide members also brings a balance by ensuring the board sees the big picture.Murman withdrew her plan Wednesday, which was the right move, given how it was sprung on the board and the public, and given the divisive reaction it caused.