The controversy unfolded last week and has the two major political parties pointing fingers. The state doesn't know how many calls were made, but complaints have come in from throughout the state, Atkins' spokeswoman Molly Woon said Monday.
"We're trying to figure out who's behind it and if there's anything illegal going on," Woon said.
The state Democratic Party blamed Republicans, alleging they were sending calls to nonafilliated and Democratic voters and therefore were trying to suppress their votes.
"For the Oregon Republican Party to tell 'active voters' that they're 'inactive voters,' and thus may not qualify to vote, is no small error and could clearly interfere with an active voter's perceived right to vote, and their belief that they can vote. This is clearly voter suppression," state Democratic Party chair Frank Dixon said.
The state Republican Party said it has issued some of the calls, but that they are intended only to alert previously registered Republicans that their registration may have fallen inactive.
State GOP Chairman Bill Currier objected to the way Atkins, a Democrat, and the state Democratic Party has characterized its efforts. Currier accused Atkins herself of trying to suppress Republican votes, saying she's urged voters to ignore the calls.
"We are deeply concerned that the secretary is actively discouraging registered Republicans who happen to be of inactive status from obtaining a ballot," Currier said in a news release late last week. "Her job is exactly the opposite -- which is to help these voters in any way possible."
Callers have reported differing language, suggesting that not all the calls are the same, Woon said. The state GOP also said it is not the only one sending messages. "Scores of other groups are making thousands of calls, though," the state GOP said on Twitter.
The Republicans said their phone message, in part, said: "Voter registration records have been reviewed in your county and there is a possibility that you or someone in your household may have had their voter registration marked inactive. If you have not received your ballot yet, this may be the reason. The Oregon Republican Party wants you to be able to vote in next Tuesday's election."
Some other messages, whose origins are unclear, say more emphatically that the recipient's voter registration is inactive, Woon said.
"The concern is that there are people we're hearing from that are in fact registered voters," and that they are worried that their vote won't count when they turn it in, Woon said.
Oregon is one of three vote-by-mail states -- there are no polling places on Election Day. Registered voters receive ballots by mail -- though they can pick up ballots at county election offices if they're away from their address. They have until 8 p.m. local time to drop their ballots at various drop boxes.
Atkins' message to voters is if they received a ballot by mail, they are properly registered, and they need not worry that their vote won't count, Woon said.
The Oregon GOP took its argument to social media.
Brian Halvorsen, who says he is exploring a Green Party run for the Oregon legislature, tweeted that it wasn't surprising that the Oregon GOP "would try to suppress the vote." And the state's official GOP Twitter account responded: "Hey Brian, explaining to inactive voters how they may cast a ballot is not suppression. Strange you need that explained."