Former Oregon Govs. Barbara Roberts and Ted Kulongoski today called on state Rep. Knute Buehler (R-Bend), the Republican candidate for governor, to release his full tax returns.

"Serving the people of Oregon is a privilege," Roberts said at a press conference at Revolution Hall. "Whether you are paying your fair share of taxes should be the first bar you cross—not the last."

Roberts and Kulongoski, both Democrats, support incumbent Gov. Kate Brown but this morning's event was the result of what appears to be a significant, unforced error on Buehler's part that was reported over the weekend by the the Oregon Capitol Bureau, a collaboration of the EO Media/Pamplin Media and Salem Reporter.

The organization reported that Buehler, an orthopedic surgeon, and his wife, Dr. Patricia Buehler, an eye surgeon, purchased $100,000 worth of Oregon business energy tax credits (BETCs) for $67,000 sometime around 2008.

That is a smart, legal and legitimate investment, as Kulongoski noted today.

"There's nothing wrong with tax avoidance," Kulongoski said.

The problem—and the opening Buehler created—is that as a lawmaker and candidate he has blasted the state's administration of the BETC program, which cost nearly $1 billion in foregone tax revenue and put easy, risk-free profit in the pockets of investors who purchased them to offset state tax liabilities.

Buehler described the BETC and similar programs in a 2017 op-ed he wrote for The Oregonian as "tax credit giveaways that mostly benefit out-of-state corporations and well-heeled investors at the expense of Oregon taxpayers, and more important funding priorities like K-12."

He probably should have disclosed he was one of those well-heeled investors.

In response to questions from Capitol Bureau reporter Claire Withycombe, Buehler's campaign issued a statement:

"The Buehlers purchased tax credits years before he was a lawmaker and before state mismanagement of the program forced the legislature to repeal the program," campaign spokeswoman Monica Wroblewski said.

Buehler's non-disclosure of his BETC investment resurrected questions about his personal finances.

Earlier this year, Buehler told The Oregonian that he had 15 corporations. But when he released his tax returns to the media—showing about $1 million in joint income for him and his wife—he did not include schedules and other supporting information that would show the source of all of that income, nor the deductions or credits he might have used to reduce his tax burden.

Jordan Conger, an aide to Buehler, says the campaign is considering requests for further disclosure of Buehler's returns.