The outcome may not be known until late Friday, and will not be officially certified until weeks later.
Both Carr and Rosen have backed off from conceding or declaring victory in the hard-fought race.
In an election night marked by excruciatingly slow posting of results, the final tally wasn't announced until just past 2 a.m. — giving Rosen a 2,217-vote edge in the D.A. race.
Throughout the night, scores of supporters at election-night parties in south San Jose talked among themselves as results, projected on screens, remained unchanged for long periods.
But there was no visible announcement on the Registrar of Voters' website page listing totals that there were thousands of votes yet to be counted. Initial results were listed as mail-in totals.
By Thursday midday, Rosen had amassed 97,214 votes, or 50.45 percent of the votes, to Carr's 95,490 votes, or 49.55 percent — giving Rosen a 1,724 lead.
Carr was gracious in her apparent defeat as the totals showed a widening lead for Rosen in the last announcements preceding the 2:03 a.m. "final" results of all precincts reporting.
She made a brief statement that could be used whether she won or lost: "We ran an honest and honorable campaign," she said. "I'm proud of the support we have had, and I'm proud of accomplishments we've made as I've been D.A."
Rosen, in a written statement, said the election is not just about him but about broader issues, including justice. But references to his apparent victory turned out to be premature in light of the huge number of uncounted ballots.