PORTLAND, Ore. - Authorities said Friday they were investigating suspected ballot tampering by an election worker in one of Oregon's most populous counties.
Clackamas County Clerk Sherry Hall said a criminal violation of election law was uncovered by her office Wednesday and reported to the secretary of state's Elections Division.
Hall declined to identify the worker or describe the specific nature of the violation.
"We are taking the situation in Clackamas County very seriously," said Secretary of State Kate Brown in a statement released Saturday. "It is extremely troubling that they have a county election employee accused of ballot fraud."
Brown said she spoke to the Attorney General about the accusation and said she wants to see the case prosecuted to the fullest extent of the law.
Additionally, Brown said every ballot the election worker had access to will be reviewed.
Oregon was the first state to conduct elections exclusively by mail, and this is the fourth presidential election in which the system has been used. Despite initial fears that the method would lead to fraud, allegations have been rare.
Because it's a criminal matter, the Elections Division referred the case to the state Department of Justice.
"We can confirm we are currently investigating criminal felony violations of Oregon's election laws, which allegedly took place in Clackamas County and allegedly involved a temporary county elections employee tampering with cast ballots," said Jeff Manning, a department spokesman.
He said the agency realizes the timing of the allegation is concerning, and it hopes to resolve it quickly.
The Secretary of State's Office announed Sunday that Bredna Bayes, the deputy director for elections in Oregon, will oversee ballot processing by the Clackamas County Elections Division.
Brown's office also sent an observer Friday to monitor ballot counting in the county, said Andrea Cantu-Schomus, a spokeswoman for the secretary of state.
The monitor, Fred Neal, will observe the process and report any irregularities but won't have direct authority, Cantu-Schomus said. That power will stay with the county clerk, she added.
Officials wouldn't say how extensive they suspect the tampering might have been. About 95,500 of the county's 228,000 registered voters had returned their ballots as of Thursday.
Clackamas County is home to 10 percent of Oregon's registered voters, and is almost evenly split between Republicans and Democrats, It's considered a swing county that is pivotal in deciding close statewide races. Three neck-and-neck legislative races could be decisive in determining which party controls the state House.
The Willamette Week newspaper reported the election worker filled in Republican bubbles on ballots where preferences had been left empty by voters in the county, which primarily comprises Portland suburbs.
A person with knowledge of the investigation said Willamette Week accurately described the incident. The person was not authorized to discuss the matter and spoke to The Associated Press on the condition of anonymity.
Democrats were angry about the reports of potential manipulation benefiting Republicans, saying even a small number of affected ballots could have widespread implications.
"This isn't just a Clackamas County issue, this is a statewide issue because this could determine who has the majority in the Oregon House for the next two years," said Rep. Tina Kotek, the House Democratic leader in charge of her party's effort to win House races.
The House is currently tied 30-30 between Republicans and Democrats, so each party would need to swing just one district to grab the majority and dictate the agenda in the Legislature for the next two years. And legislative races are sometimes close - a Clackamas County Senate race was decided by 227 votes in 2010, and another in southern Oregon by 275 votes.
A Republican effort to stop Portland liberalism from creeping into Clackamas County has emerged as a dominant theme in its recent elections.
Chris Edmonds, campaign manager for county Chairwoman Charlotte Lehan, a Democrat, said the campaign would be talking to attorneys as it explores possible legal action.
"We don't know whether this was an individual acting alone or if this was part of a coordinated effort," he said.
Lehan's opponent, Republican John Ludlow, emphasized that an allegation is not proof of guilt, but "if they did it, it was dead wrong."
Edmonds noted that up to 30 percent of voters focus solely on the major races, such as U.S. president, and skip county commission and other local races, meaning tens of thousands of voters may not have participated in the Lehan-Ludlow race. Given that the race is expected to be tight, even a few illegal markings could decide it, he said.
"We may not be able to know the full extent of the fraud, and that's what we're trying to know," Edmonds said. "When someone's just filling in a bubble, how can we go back and know the true intent of the voter?"
Late in the afternoon, Sherry Hall, the Clackamas County clerk, told KATU.com that there's no way to know which voter or voters are affected because the ballots are secret; however, the tampering was obvious.
KATU.com staff contributed to this report.
Associated Press writer Jonathan J. Cooper contributed from Salem, Ore.
Copyright 2012 The Associated Press.