If President Trump, or anyone else, wants to get on the New Jersey ballot to run for president in 2020, he could have to release his tax returns, if some Democratic lawmakers have their way.

Whether legislators have that power was an open question Monday, as the Assembly Judiciary Committee advanced a bill that would require candidates for president and vice president to disclose their federal income tax returns in order to appear on the state's ballot.

"Anybody who tells you they know whether it's constitutional or not is not correct," Rick Hasen, an election law expert and professor at the University of California, Irvine, said of a state's ability to require tax-return disclosure to get on the ballot.

The bill's sponsor, Assemblyman John McKeon (D., Morris), acknowledged that the proposal raised constitutional questions, but argued that such laws would likely be upheld "prior to the election four years from now."

New Jersey is the latest state to propose a requirement that presidential candidates release their tax returns, after Trump broke 40 years of precedent by not doing so.

As of Saturday, lawmakers in 17 states had introduced bills that would require presidential candidates to release federal tax returns to get their names on state ballots, according to the National Conference of State Legislatures.

While disclosing returns had not been an issue in the past, "we shouldn't downplay the Trump effect" in motivating state legislation, said Vikram Amar, dean of the University of Illinois College of Law.

"If another candidate other than Donald Trump had not turned over his tax returns, maybe this issue wouldn't have this much traction," Amar said, noting Trump's wealth and business holdings.

In New York, a Democratic state senator in December introduced the Tax Returns Uniformly Made Public Act — or TRUMP Act.

Other states where legislation on tax-return disclosure has been introduced include Arizona, California, Connecticut, Maryland and Pennsylvania, where State Sen. Daylin Leach (D., Montgomery) is a bill sponsor.

In nearly every state with proposed legislation on the issue, Democrats sponsored the bills, though Republicans did in Kansas and Minnesota.

In New Jersey, McKeon, who chairs the Judiciary Committee, said, "There's no doubt about it" that the November election motivated him to sponsor the bill.

But "it obviously has no impact on the last election," McKeon said. He said the bill was a matter of transparency: "We want to know the sources of income for those running for the nation's highest office," as well as potential conflicts of interest, charitable giving, and use of tax shelters.

The New Jersey legislation would require presidential and vice presidential candidates to disclose their federal income tax returns for at least the five most recent taxable years for which they have filed returns with the IRS.

Candidates would have to file those returns with the state Division of Elections at least 50 days before the general election, under the bill.

The bill has not been introduced in the Senate. Senate President Stephen Sweeney (D., Gloucester) said the Senate would move forward with the legislation if he determined it was legal.

"The president shouldn't be hiding his tax returns," Sweeney told reporters Monday.

A spokesman for Gov. Christie declined to comment on the bill.

The bill, if enacted, would likely face a legal challenge, as would laws passed in other states, Amar said. But he said it was hard to predict the outcome.

While the Constitution gives the federal government power to regulate congressional elections, "states are given a lot more leeway" in presidential contests, he said.

Amar noted the U.S. Supreme Court's 2000 Bush v. Gore decision, in which several justices, considering the Florida legislature's move to pick electors itself, "didn't think that was out of bounds."

"Presidential elections are very decentralized," Amar said.

But states lack the power to alter the qualifications of the president, which are established in the Constitution, Hasen said. "The question is whether or not this requirement would be setting an unconstitutional qualification," he said.

If states established other disqualifying criteria — not having previously held public office, for instance — the names on ballots could differ greatly from state to state, Amar said.

In that case, "no one's going to win the Electoral College, no one's going to get more than 50 percent of the electors," he said. "The whole idea of a nationally elected president ... would tend to fall apart."

But the impact of legislation such as the bills requiring tax-return disclosure could depend on which states pass it: If only blue states did, for instance, a future Republican would not necessarily be encumbered, Amar said.

New Jersey's bill cleared the judiciary committee Monday with support from five Democrats. Two Republicans voted against it.

"Sharing your concerns about the constitutionality, no," said Assemblyman Michael Patrick Carroll (R., Morris) as he voted against the measure. Carroll had proposed amending the bill to also require gubernatorial and legislative candidates to disclose their tax returns, but Democrats on the committee delayed a vote on his motion.

McKeon said he wasn't concerned, because he believed the bill would be upheld. "But I can understand why one might argue to the contrary," he said.