Bishop's camp said the incumbent led by 15 votes as the counting of absentee ballots finished for the week. He had trailed by 383 votes when the count of absentee ballots began Tuesday.
Altschuler's camp said the margin was 14 votes. Counting has been completed in East Hampton, Riverhead, Shelter Island, Smithtown, Southampton, Southold, as well as 41 of 294 election districts from Brookhaven, but there also are hundreds of contested ballots in those districts that were set aside.
Altschuler has challenged 736 ballots while Bishop has challenged 524, according to Bishop's camp. Altschuler's camp said they had challenged 714 ballots and Bishop 496.
"We've had four days of counting and each day we've gained," said Bishop spokesman Jon Schneider late Friday. "We're excited to be in the lead."
Rob Ryan, Altschuler's campaign manager, said Bishop is underperforming where he should be strong. "Counting absentee ballots is similar to a roller-coaster ride. Over 5,000 ballots remain to be counted in Brookhaven and we remain confident that when the final vote is counted, Randy Altschuler will be the new congressman."
One of the challenges by the Altschuler forces was to the absentee ballot of Michael Foley, son of lame-duck state Sen. Brian X. Foley (D-Blue Point). Republicans contend Foley, 21, a student at George Mason University in Virginia, was not a legal resident of the district.
In Nassau, GOP challenger Jack Martins holds a 403-vote lead over incumbent Democrat Craig Johnson in the 7th Senate District - one of three races that will decide which party will control the state's upper house for the next two years.
The counting of the undisputed absentee ballots in that race finished Thursday, but 879 contested ones remain. Johnson would need to win about three-quarters of them to overtake Martins, the mayor of Mineola.
Justice Ira Warshasky, who has oversight of the Nassau election results, issued an order late Friday that appointed special referee A. Jeffrey Grob to conduct a hearing at the Board of Elections office in Mineola on Monday in a bid to reduce the number of contested ballots.
Suffolk seemed to be handling its machine audit with few problems, but Republicans and Democrats were fighting in Nassau and some officials said it was likely that the issue will end up in court at some point because the Martins-Johnson race so close.
Democrats said Friday numerous problems had been discovered in the audit of the first half-dozen machines, out of 32 to be audited. "[The] number of untallied votes could possibly reach 4,000 and affect the final outcome," a Johnson aide said.
But Republicans denied there was a significant problem. "The audit is proceeding and it is accurate. We have found no discrepancies that did not have a logical explanation," said John Ryan, attorney for the Republican elections commissioner.
Correction: A previous version of this story gave an incorrect age for Michael Foley.