Lawmakers in several deep-blue states want to require presidential candidates to release their tax returns in order to appear on the ballot in those states, a sharp rebuke of President-elect Donald Trump's ongoing refusal to make his tax records public.

A pair of Maryland Democrats on Tuesday announced they would introduce a bill mandating the release of five years of tax returns, mirroring similar proposals in New York, Massachusetts, California and Maine.

If approved, the proposals could keep Trump from appearing on some ballots in 2020 if he continues breaking with the decades-long tradition of financial transparency and decides to seek a second term.

U.S. Sen. Ron Wyden (D-Ore.) in May introduced a federal bill requiring major-party candidates to release their returns, but that legislation didn't advance in the Republican-controlled Congress.

The state lawmakers say they want to enshrine into law what's been a long-standing norm among presidential contenders: the public release of tax returns detailing sources of income, business interests and charitable giving.

Trump faced strong criticism from his opponents throughout the 2016 campaign for saying he would not release his tax returns while the Internal Revenue Service is auditing them. The IRS does not bar public disclosures of tax returns under audit - Richard M. Nixon released his as president, despite being under audit. Portions of Trump's 1995 tax return, which were leaked to the New York Times, suggest that the president-elect may have avoided paying federal income taxes for as long as 18 years.

"We all expected anyone who is going to be in front of the public and lead our nation would be transparent," said Maryland Sen. Paul G. Pinsky, who plans to sponsor the legislation with Del. Jimmy Tarlau, a fellow Prince George's County Democrat. "He chose not to be, and we want to make sure that doesn't happen again in the future from any candidate."

It is not yet clear whether the proposal will win support from the legislature's Democratic leaders or is likely to advance in either chamber. Spokespeople for Gov. Larry Hogan, a Republican who did not vote for Trump, did not immediately return a request for comment on whether he would sign such a bill if it passed.

Senate Minority Leader J.B. Jennings (R-Baltimore County) said it should be up to voters to decide if they don't want a president who hasn't disclosed tax returns.

"To me, it just looks like sour grapes over the election," said Jennings. "We don't reveal our tax returns as legislators. Why are you doing it for the president and not every other office too?"

The states mulling this approach to pressure Trump into releasing his taxes all went to Democrat Hillary Clinton in the presidential election, and the failure of Trump or any other Republican to appear on their ballots would not necessarily affect the result of a future election.

But lawmakers pushing the tax-returns mandate say the significance of a sitting president, or any major-party candidate, not being offered as a choice to voters in their states would ramp up the pressure on White House hopefuls to disclose their finances.

"It would be astounding if a presidential candidate refused to file for office in any state in the union . . . and also suggest the candidate has something to hide," said New York state Sen. Brad Hoylman, a Democrat who was the first to author a tax-returns disclosure bill.

He called the legislation the Tax Returns Made Uniformly Public, or TRUMP, Act.

States have varying rules for how candidates can get on the ballot, but they generally focus on submitting signatures and paying fees. Additional qualifications or disclosures are unusual.

Hoylman and other lawmakers say Laurence Tribe, a constitutional-law scholar at Harvard University, told them requiring tax disclosures would be constitutional under the broad powers that states have to control ballot access. Tribe did not immediately return an email seeking comment.

Vikram Amar, the dean of the University of Illinois College of Law, said that a patchwork of ballot access requirements in states that leave voters in different states with different choices in a national race could violate the Constitution. But he also said tax disclosure rules could stand if courts agree that states have wide latitude even in running presidential elections. Such a decision could also open the door for other requirements - such as a barring candidates such as Trump who have never held public office or politicians who have been in office for decades, Amar said.

"You could imagine states doing all kind of things that may be nominally legitimate but obviously have a partisan tinge to them," Amar said in an interview.

Lawmakers pushing for tax-return disclosure say they aren't proposing anything radical, since candidates in every presidential race since 1980 - except Trump - have released their tax returns.

"This is a real opportunity for statehouses to take this matter into their own hands and ensure that their voters have the information they need to make a decision as important as casting a vote for president of the United States," Hoylman said.

The Maryland General Assembly's 2017 legislative session begins Jan. 11.