Election night totals show Laesch trailing Democrat Bill Foster by less than 400 votes. The race will determine which of them gets to face Republican Jim Oberweis in the November general election to replace Hastert in Congress.
Laesch already has conceded to Foster for a March special election that will fill the rest of Hastert's current term.
But Laesch says he's waiting for any outstanding provisional and absentee ballots to be counted before deciding about the general ballot.
Election law calls for the results to be certified by March 7th.