Karen Brown, a former Catholic-school teacher who joined the Republican Party just this year, has solidified her narrow lead in the race for GOP's mayoral nomination over real estate agent John Featherman, according to unofficial returns.

Brown had a 57-vote lead over Featherman after Philadelphia election officials tabulated the returns from voting machines, and the margin grew to 58 votes Tuesday with the count of absentee ballots. Brown had 81 votes from absentees, Featherman 80.

All that remains to be counted are provisional ballots, cast by voters who showed up at the polls on primary election day May 17 but were not listed as registered voters in the materials distributed in advance to the city's voting places.

Kevin Richardson, supervisor of electronic activities for the City Commissioners' Office, said about 50 registered Republicans citywide submitted provisional ballots - not enough to overturn Brown's lead even if they all voted for Featherman.

Richardson said it would likely be Thursday or Friday before a final count was completed.

Featherman is not throwing in the towel. "This election has not been decided yet," he said Tuesday. "This is such a close race, with so much at stake, I'm not going to give up until every vote has been counted."

Brown, who had been interested in running for City Council as a Democrat, changed party to run for mayor with support from the Republicans' embattled local leadership, general counsel Michael P. Meehan and Chairman Vito Canuso.

She said Tuesday she was looking forward to campaigning against Mayor Nutter instead of fighting GOP dissidents, who were backing Featherman.

"On many levels, this was a disgrace," Brown said. She said the party dissidents "remind me of unruly kids who need a timeout . . . but I'm not as upset with them as with the news media, for playing into it. . . . I'm glad it's over, and now we can really fight for the city, and that's what I want to do."

Brown, 50, is married and the mother of three children now in their 20s. A native of the Southwark section of South Philadelphia, she said she has lived within blocks of 10th and Mifflin Streets her entire life. She graduated from the former St. Leonard's Academy at 33d and Market Streets, then earned bachelor's and master's degrees in business from Gwynedd-Mercy College.

Brown said she spent 21 years as a math and science teacher at two archdiocesan schools, St. Casimir's in South Philadelphia and St. Anne's in Port Richmond, then worked in the City Commissioners' Office as assistant to the budget director from 2005 until 2009.

Contact staff writer Bob Warner at 215-854-2611 or warnerb@phillynews.com.