It’s a familiar campaign tactic: seeking to make opponents look bad by accusing them of not casting ballots.

Most recently, U.S. Senate candidate Monica Wehby was criticized for supposedly voting less than half the time.

Locally, John Hummel said during the recent campaign for district attorney that incumbent Patrick Flaherty had missed voting in 16 elections over 20 years.

It’s rarely, if ever, the right way to judge a candidate’s qualifications for office, but a recent report suggests it might also be inaccurate, depending on the source of the data.

Look up Oregon Senate President Peter Courtney’s record on the Secretary of State’s website, for example, and it shows he didn’t vote in nine Oregon elections. But, according to a report from Anna Staver of the (Salem) Statesman Journal, that’s not true. In fact, she reported, he’s never missed an election in which he was eligible to vote.

The problem lies in the various ways records were kept across the state before the Secretary of State’s Office created its Oregon Centralized Voter Registry in 2006. The new state system says a person didn’t vote if he or she didn’t return a ballot. But in some counties before 2006, people were listed as not voting in some elections where they weren’t eligible to vote. Those records were incorporated into the state’s system, the Statesman Journal said, meaning pre-2006 information isn’t necessarily dependable.

The Secretary of State’s Office doesn’t plan to try to correct that pre-2006 data, so accurate reports require more digging than just a quick check of the statewide website. In the Wehby case, if the pre-2006 records are deleted, the Statesman Journal reported, her voting record goes from 44 percent to 63 percent. Flaherty’s figures were unaffected by the issue because Deschutes County uses the same standard as the Secretary of State. A Bulletin examination showed the votes Flaherty missed were all special elections, not general elections.

More and more data has become available in this electronic age, compounding the challenge of ensuring it means what we take it to mean. Curiosity and an open mind are critical tools in making sense of it all. Sadly, those tools are often in short supply in campaign offices.