Last month, the Inquirer reported on the statistically improbable rise since 2008 in independent voters or those unaffiliated with either of the county's major political parties.
Nearly half the county's 30,000 new voters since 2009 have shown up on voter rolls as unaffiliated or associated with a minor party - a good deal more than in any other county in the state.
By comparison, such voters account for fewer than 29 percent of new registrants in Philadelphia, Bucks, Chester and Delaware Counties, according to data from the Pennsylvania Department of State.
The vast majority of those new voter registrations came in through PennDOT's motor voter program, a computer system that allows users to register to vote or update their registrations while applying for or making changes to their driver's license.
In a statement released Friday, Department of State spokesman Ronald G. Ruman said that a thorough investigation of the motor voter system had determined that it was working correctly at all PennDot driver's license centers in Montgomery County. He placed the blame on human error in the county's Voter Services Office.
Hoeffel said that he was notified late yesterday that the office had determined one of its employees was responsible for the confusion.
He explained that when residents change their address for their driver's licenses at PennDot, they are also offered the option of changing it on their voter registrations.
If they accept - even if they were never registered to vote in the first place - the information is submitted to the county's voter services office for updating the voter rolls.
Beginning in 2008, Hoeffel said, a county employee added those names coming through without prior registrations to the voter rolls as independents because there were no party affiliations for them on file. The worker should have discarded them since they had never officially registered to vote in the first place, Hoeffel said.
It remained unclear Friday whether only those who were not previously registered to vote were affected or if others who had used the motor voter system to change their addresses may also have seen their party affiliations change.
Earlier this week, state department officials sent the county a list of 3,200 voter registrations that it had flagged as suspect.
County Voter Services Director Joseph Passarella could not be immediately reached for comment.
Hoeffel assured all voters that should they run into problems at the polls during Tuesday's primary, election workers were prepared to offer them two options.
They can come to Norristown to seek a county judge's order allowing them to vote or they can fill out a provisional ballot at the poll. Voter services staff will investigate all provisional ballots after the election to determine whether they should count, Hoeffel said.
"I am confident that no voters have been disenfranchised by this error and that Tuesday's Primary Election will run smoothly," Hoeffel said.
Contact staff writer Jeremy Roebuck at (267) 564-5218 or at firstname.lastname@example.org.
Follow the Inquirer at www.Twitter.com/PhillyInquirer and www.Facebook.com/PhillyInquirer