The spending surge reflects how competitive the second slot has become. In San Francisco's ranked-choice system, a strong second-place showing can be as strategically significant as a first, particularly when a leading candidate has locked up a base but not a majority.

Neither campaign has released updated expenditure totals publicly as of this writing. The scale of the burn rate — described as furious by Mission Local — suggests both operations are pulling hard on direct mail, digital advertising, and field in the final days before the June election.

Chakrabarti, a former congressional aide who ran Bernie Sanders' 2016 digital operation, and Chan, a current member of the Board of Supervisors representing District 1, are competing in a race where name recognition and ground infrastructure both carry weight.

What to watch: Campaign finance filings due after the election will show exactly how much each candidate spent and where the money went. The results on election night will determine whether the spending paid off — and whether either candidate secured enough of a foothold to matter in a runoff scenario.