"Before we make any official announcement, we want to make sure all the votes are counted," Thomas said.
A spokeswoman for the Los Angeles County registrar/recorder said they wouldn't have a firm number of uncounted ballots in the special-election race until at least Thursday, with vote tallies no sooner than Friday.
There are 149,174 outstanding ballots countywide that have yet to be processed, according to the registrar.
Preliminary totals have the current gap between candidates at 6,155 votes, which would likely require that all of the remaining uncounted ballots go for Ramani.
Still, Thomas said he had heard from a number of Republican voters that they had received their absentee ballots late, so a significant portion could swing to Ramani.
"I don't know if it will change the outcome of the election, but it will certainly tighten it up," he said. "We are going to wait until we have all the facts."
Meanwhile, Gatto flew to Sacramento on Wednesday to start the transition. He said he expected to take the oath of office in the next two weeks.
"I think that in this era of term limits, almost every day that you can use to learn the system and understand the process is valuable and should be taken advantage of," he said on his way to the airport.
The Assembly district's former representative, Paul Krekorian, whose Los Angeles City Council district includes overlapping areas, released a statement Wednesday congratulating Gatto on the win.
His endorsement for the race, Glendale school board member Nayiri Nahabedian, dropped out of the race after losing to Gatto in the April primary.
Voters now have roughly four months to prepare for yet another election for the seat's full two-year term. When the election in November is all said and done, voters will have been asked to vote four times for the same seat in about six months — a process that both candidates have said contributes to voter fatigue and confusion.
"It was a confusing mess from the beginning," Thomas said. "This is only fitting to finish the election this way, I suppose."