At 11:20 last night, City Commissioner Stephanie Singer was at 999 signatures - one short of the 1,000 required to remain on the May 19 Democratic primary ballot, but her legal team was reviewing 18 signatures to see if they could resurrect just one.

Singer, who was first elected a city commissioner in 2011, saw the number of her signatures whittled down from nearly 1,500 when the ballot-challenge process started last week.

She was challenged by Daniel Bucher, who is not a candidate. Petition challenges, typically, are filed by people acting on behalf of political rivals of those being challenged.

Unfortunately for Singer, her petitions didn't add up. And that's kind of ironic, given that she has a bachelor's degree from Yale University and a doctorate from New York University - both in mathematics.

The former Haverford College mathematics professor has published two books and previously served as leader of the city's 8th Ward, according to her bio posted online by the nonpartisan government watchdog group the Committee of Seventy.

As a member of the Board of Elections, Singer is one of three elected commissioners responsible for administering voter registration and conducting elections.

While campaigning for the job in 2011, she pledged to make rooting out corruption one of her goals.

In addition to Singer, those running for the three commissioner seats include incumbents Anthony Clark, a Democrat and the chairman of the board, and Al Schmidt, the lone Republican. Seven challengers are also seeking those seats.