AUGUSTA — A new proposal would require those seeking to appear on a Maine ballot for president or vice president to make public their federal income tax returns for the past five years.

Rep. Seth Berry, D-Bowdoinham, said Monday it had been a sort of unwritten law for decades that contenders for the nation’s top job disclose their tax forms.

But last year, Republican Donald Trump refused to follow tradition because, he said, he couldn’t release the forms until the Internal Revenue Service completed an audit of his returns.

Trump’s move has spurred lawmakers in more than half of the states to consider legislation to require candidates for president to hand over their tax forms if they want to appear on the ballot. So far, none of the measures has passed, but Berry said that in some places, such as California, they stand “a very good chance.”

Berry, who co-sponsored the bill in Maine, said he’s not sure what its fate will be.

He said the idea shouldn’t be a partisan issue but acknowledged some will see it that way. He said, though, that he expects some “principled Republicans” will back it.

“Regardless of how the conversation ends, it’s important to begin it,” Berry said.

He said people have come to realize that “the stakes are too high” for a president who can put the nation’s “blood and treasure” on the line to have undisclosed conflicts of interest. He said voters “deserve transparency” before casting ballots for an office so important to the country.

One big hitch for those pressing for a required tax form release is that the U.S. Supreme Court might nix the notion. It  has ruled in the past that states can’t go beyond the minimal qualifications listed in the Constitution for ballot access, basically age and citizenship.

The proposal, which hasn’t yet been sent to committee, would direct the secretary of state to post the tax returns on the department’s website. The forms could be redacted to have only the candidate’s name and no other personal information, such as an address or Social Security number.

The bill also includes a provision to have the secretary of state report on how Maine might also require the tax forms of presidential primary candidates in the future.

A number of legislators are signed on as co-sponsors of the bill, including Sen. Shenna Bellows, D-Manchester, and Rep. Gina Melaragno, D-Auburn.