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San Leandro mayoral candidate Stephen Cassidy, left, greets supporter Carlos Jacome, right, during an election night party on Tuesday, Nov. 2, 2010, in San Leandro, Calif. (Aric Crabb/Staff)

SAN LEANDRO -- Incumbent Mayor Tony Santos is running out of time to challenge election results showing Stephen Cassidy narrowly edging him out for the mayor's seat.

The Alameda County Registrar of Voters certified the election results late Friday afternoon, meaning Santos only has until Wednesday -- five days after certification -- to challenge the results.

Santos, thus far, has declined to concede the race, saying he has concerns with the ranked-choice voting process that was used for the first time in the city's elections this month.

Charles Gilcrest, Santos' campaign adviser, said Santos is in Germany on vacation and will not return until Wednesday. However, he added Santos has not made a decision on whether to challenge the certified results.

"Tony is waiting to evaluate everything," Gilcrest said.

The certified results show Santos trailing former school board trustee Cassidy by 232 votes. Cassidy finished with 50.6 percent of the vote, while Santos had 49.4 percent.

Santos, who was a strong supporter of the city switching to ranked-choice voting when the decision was made nearly 10 years ago, said earlier this month he was not sure how far he wants to push questioning the election. Nevertheless, he said he still was concerned with how the ranked-choice voting system played out and how votes are redistributed.

Dave Macdonald, the county's registrar of voters, said anyone may ask for a recount but must pay for the entire process. He added that recounts do not really differ from the way his office does the original count, but anyone still may ask for a second count.

Macdonald said he did not have a good idea of the cost of a recount. Any type of recount would cost in the thousands of dollars, election officials said.

Ranked-choice voting -- also known as instant-runoff voting -- allowed voters to rank their first-, second- and third-choice candidates for a single office. If no candidate receives more than 50 percent of the vote when ballots are tallied, the ranked-choice voting system kicks in. The system starts eliminating candidates from the bottom up. When a voter's first choice is eliminated, their second choice is then counted.

This process of elimination occurs until a candidate has 50 percent of the vote.

The system eliminates the need for a primary.