If poll numbers were grades, San Francisco Mayor Ed Lee would be at the bottom of the class.

Lee, whose second term has been haunted by growing traffic congestion, homeless encampments and skyrocketing rents, scored a 30 percent job approval rating in a recent Public Policy Polling survey.

Lee’s negatives were at 50 percent, with 19 percent unsure.

The findings from the Oct. 3-4 survey by the North Carolina-based outfit are the lowest private polling numbers on the mayor’s performance we have seen since his re-election in 2015. The survey of 501 likely voters had a margin of error of 4.4 percentage points.

On the bright side, Lee is doing a lot better than President Trump. His approval rating in the city isn’t underwater, it’s at the bottom of the sea — 13 percent favorable to 83 percent who disapprove.

The Lee and Trump ratings were part of a more extensive poll commissioned by backers of a proposed ballot initiative calling for the city to hire lawyers to help tenants fight evictions.

On that question, the tenants are the clear winners — 60 percent of those surveyed say they would support the measure.

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross