Liberal Dave Sharma has appealed to small business and retirees in the battle for Wentworth, warning a vote for independent Kerryn Phelps would hurt the economy and cut their savings.

As voters prepare to go to the polls in Saturday's byelection, local Liberals say a hamstrung campaign and shambolic week in federal Parliament could see a major political upset, reducing the Morrison government to minority and adding a charismatic independent to the crossbench.