The mall's current owner, Unibail-Rodamco-Westfield, which acquired the five-level mall in December, said it doesn't comment on market specualtion or rumors.
Stockdale did not immediately return a call seeking comment.
Recent city memos allude to efforts by Unibail-Rodamco-Westfield to sell the five-level mall.
The potential sale came to light because the city is restructuring how it financed the Horton Plaza Park. A City Council memo and Civic San Diego staff report related to the move say there is a future proposed purchase and sale of Horton Plaza shopping center to a new entity.
A report released Monday by the city's Independent Budget Analyst says this is a key time for the city to redo the agreement given the current efforts by the owner to sell the property - and improve negotiating power if there is redevelopment.
City Independent Budget Analyst Andrea Tevlin called the potential sale the million dollar question at City Hall.
Gary London, a San Diego commercial real-estate consultant, who may be involved with the deal, said the mall is definitely in play.
"It was down two suitors, and my understanding is that one has it tied up, pending some deal points," he said. "It is my understanding that details will be announced soon."
Jason Hughes, CEO of Hughes Marino, who is not involved in the deal, said Stockdale went non-refundable with its deposit about a week ago. It is considering turning the old Nordstrom building into creative office space.
Horton Plaza has recently seen longtime shops close, including Nordstrom, which hindered foot traffic on the southern wing of the mall.
Plus, Jimbo's grocery store recently filed suit against the mall alleging it is not being maintained adequately, costing it business.
(Correction - An earlier version of this story incorrectly referred to the company buying Horton Plaza as Stockdale Investment Group. However, Stockdale Capital Partners is in escrow to buy the property)