CARACAS, Venezuela (AP) — With President Hugo Chavez in his tightest re-election race yet, some of his opponents are warning that the use of thumbprint readers at Venezuelan ballot boxes could scare away voters, adding to fears about the fairness of the Oct. 7 vote.

The country’s electoral council has long used fingerprint scanners at the entrance to polling places to ensure voter identification. But this year, the readers will be hooked to the electronic voting machines themselves. Citizens must press down a thumb to activate the ballot system.