Wiener had 87,641 votes (55.4%) to Chan's 70,511 (44.5%), per KQED's 11:53 p.m. update, which estimated 51.42% of votes counted. ABC7 showed the same totals and headlined its live coverage with Wiener and Wahab leading their congressional races.
The AP had not called the race in either source as of Wednesday morning.
KQED notes it is the first truly competitive race for the seat in years, as Pelosi retires after nearly four decades. Both candidates are Democrats steeped in San Francisco politics, a state senator and a city supervisor.
Pelosi campaigned with Chan's volunteers on Election Day. The winner will represent San Francisco in Washington on issues from foreign policy to taxation and federal regulation.
All results are unofficial election-night and early-morning counts as of Wednesday, Nov. 4. Counties keep counting mail and provisional ballots for days, and certification comes later, so margins can shift, especially in close contests.