President Donald Trump may have to release his tax returns if he wants to compete in California in 2020.
A bill passed by the state legislature Friday requires presidential candidates to release their five most recent years of tax returns to get on the ballot.
If this holds, Trump would have to submit them to the state when he runs for re-election, or he could be considered ineligible to appear on the ballot in the primary and general election.
"Our top priority is making sure the voters of California have the information they need before they go into the voting booth," Democratic state Sen. Mike McGuire -- a lead sponsor of the bill -- told CNN. "If President Trump doesn't release his tax returns voluntarily, California will do it for him."
The bill, passed mostly on party lines in both chambers with only some Republicans supporting the effort, also requires the California secretary of state to publish the returns online with personal information redacted.
Bucking a tradition that dates back over 40 years among presidential nominees in both parties, Trump has not released any tax returns publicly. He says he's under audit and will not release them before that's completed.
Advisers to the President have publicly stated he will most likely not release them, and they point to financial disclosure forms that he has filed.
California's Democratic governor, Jerry Brown, hasn't said whether he'll sign the bill from the legislature that's controlled by his own party. Democrats expect him to sign it, given its strong support.
Brown is the first governor of the Golden State in more than 30 years to not release his tax returns as well.
Democrats acknowledge this issue hasn't been tested in the courts and know Republicans will most likely challenge this bill.
"We're looking at all of our options," California Republican Party Chairman Jim Brulte told CNN. "If he chooses to run again, Donald Trump will get all of California's primary delegates to the national convention. Period."
The only eligibility requirements in the Constitution to run for president are that a person must be at least 35 years old, be a natural-born citizen and have resided in the United States for at least 14 years.
Courts will most likely have to decide whether this bill is permissible with other ballot access rules or changing the qualifications to run for office.
"A line must of course be drawn between permissible ballot access laws and impermissible attempts to add qualifications to those specified in the federal Constitution," constitutional scholars Laurence Tribe, Richard Painter and Norman Eisen wrote in support of the law. "But our research and reflection lead us to conclude that tax return disclosure laws ... comport fully with the US Constitution."
Painter and Eisen were top ethics lawyers for Presidents George W. Bush and Barack Obama, respectively.
Supporters point to conditions beyond the Constitution that are mandated by states to appear on a ballot, like filing deadlines, signature requirements and fees as analogous to a prerequisite financial disclosure form from a candidate.
"States can determine eligibility beyond the ballot as long as they're not unduly burdensome," Erwin Chemerinsky, dean of the University of California Berkeley School of Law, told CNN. "Here it's just saying that you do something that's very much within your power to do -- like getting signatures -- disclose your tax returns."
Brown has one month to sign the bill into law or veto it. If he signs it, as many Democrats hope, California could succeed where many opponents of the President have failed in getting Trump to disclose his tax returns.
CNN's Wade Payson-Denney contributed to this report.