The Boston City Council president and city clerk are splitting acting mayor duties this week while Mayor Michelle Wu takes a family vacation in Maine.

With weeks to go before the Sept. 9 preliminary election, the math remains daunting for Boston mayoral hopeful Josh Kraft.

The poll of 500 Boston voters likely to participate in the Sept. 9 preliminary election showed a wide gulf between Wu and Kraft, who drew 30 percent support to her 60 percent.