A proposal inspired by President Donald Trump's refusal to release his tax returns advanced Tuesday in Washington state. A bill in the state Legislature would require candidates to release five years of returns before they could appear on either the primary or general election ballot in the state.

Senators approved the bill on a 28-21 vote Tuesday, sending it to the House.

"Although releasing tax returns has been the norm for about the last 40 years in presidential elections, unfortunately we've seen that norm broken," said bill sponsor Sen. Patty Kuderer, a Bellevue Democrat, during debate Tuesday. Kuderer later confirmed she was referring to Trump.

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How a candidate has handled their own financial affairs and personal investments are relevant details for voters choosing a commander-in-chief, Kuderer added.

"It's become part of the vetting process," Kuderer said later.

Kuderer's proposal would apply only to candidates for president and vice president.

Presidents as far back as Richard Nixon have released their tax returns either during their campaigns or after being elected.

Trump initially promised to release his returns, but then reversed himself, pointing to an audit by the Internal Revenue Service, although experts and IRS officials have said audits don't prohibit taxpayers from releasing their own returns.

Trump's tax returns would contain information on his sources of income, how much he earned, and any strategies he used to reduce his tax bill.

But critics warned enacting the Washington proposal would invite an expensive legal fight, politicize the administration of elections, and put the state in an untenable position if a candidate defied the rule.

"We're on really risky ground when we're trying to place conditions on a federal election," said Sen. Hans Zeiger, a Republican from Puyallup.

Some also expressed a deeper unease with forcing candidates into transparency, and warned legislators could see the same expectation turned back on themselves in future elections.

"I just don't understand why in the world you would promote something that would connote that there's something suspicious about the activities of our elected officials," said Sen. Maureen Walsh, R-Walla Walla.

At least 25 states have proposed similar bills in recent years according to the National Conference of State Legislatures, spurring wide debate over whether states have the Constitutional authority to make such rules.

The U.S. Supreme Court has held that states cannot add to the qualifications of senators and congressional representatives outlined in the Constitution.

But legal experts have said the law is at least partly unclear, since the Constitution also gives states the power to set rules for how presidential elections are held within their borders.

In an advisory letter issued before Tuesday's vote, Washington Attorney General Bob Ferguson and solicitor general Noah Purcell told lawmakers they thought the proposal was legal.

"The disclosure requirement you propose is likely Constitutional," the pair wrote.

But the pair added in the same letter that because of the many possible interpretations of the law, if it passed the bill "would definitely be challenged in court."

In addition to requiring candidates to turn over their tax returns, the bill would also direct the Secretary of State to post them publicly.

New Jersey lawmakers approved a similar measure in 2017, but Republican Gov. Chris Christie vetoed it, calling a political stunt.