All those details can be fodder for campaign attack ads, explaining why many candidates are reluctant to release it.

California’s Democratic nominee, Gavin Newsom, released six years of tax returns after two straight cycles in which neither major party nominee released theirs. That gave Republican nominee John Cox a target to attack.

Cox — who released his two-page 1040 forms, but none of the attachments or schedules released by Newsom — suggested the Democrat is taking advantage of lower income taxes in Nevada and getting rich from an “intricate web of Getty-funded properties and businesses.”

A spokesman, Nathan Click, said Newsom had no regrets about releasing his tax returns, and remained “proud to have set the bar of transparency in this race.”

The release-or-not-to-release calculation has been on full display in Wagner’s uphill bid to unseat Wolf in Pennsylvania.

Wagner has said he will not divest his ownership of the $75 million waste hauling business should he win. That has raised alarms with transparency advocates about the potential for conflict because state government heavily regulates municipal waste.

He has given varied reasons for his refusal to open his tax returns for review — saying at one point it was because they were “very complicated.” At another, he said unions would use them to promote his wealth in an attempt to organize his company’s workers.

Wagner maintains that he has complied with state requirements to disclose sources of income, that he owes no back taxes and provides charitable contributions through his company. Democrats say his word is not enough.

In a statement, the state Democratic Party said Wagner’s “refusal to release his tax returns raises questions about what he could be hiding.”

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Associated Press writers Sara Burnett in Chicago, Morgan Lee in Santa Fe, New Mexico, and David Pitt in Des Moines, Iowa, contributed to this report.