President Trump has no intention of releasing his tax returns for the 2020 election. That much is clear after California took the extraordinary step last week of blocking presidential candidates from appearing on the state’s primary ballot unless they release their tax returns. And rather than release them, Trump is suing California.

“The effort to deny California voters the opportunity to cast a ballot for President Trump in 2020 will clearly fail,” Jay Sekulow, Trump’s lawyer, said in a statement Tuesday as Trump’s campaign and the Republican National Committee filed not one but two lawsuits against California over the law.

What happens next could shape an epic standoff between Trump and the most populous state in the nation. If Trump loses this lawsuit, he faces a choice: release his tax returns, or forgo running in California’s Republican presidential primary.

As evidenced by the lawsuits, he clearly doesn’t want to have to skip running in California. It almost certainly wouldn’t affect his chances at getting the nomination, because he has no credible primary challenger to take advantage of a Trump absence from the ballot in California. Former Massachusetts governor Bill Weld is running against him, but he has drawn negligible support. All the Republican Party infrastructure is behind Trump. (The law does not apply to the general election.)

But it would be unprecedented to have the incumbent president of the United States not competing in a major state primary. And campaigns don’t want to leave anything to chance. What would happen if a surprise entry got in that reshaped the Republican primary? Suddenly Trump wouldn’t be able to compete in California against that person.

Beyond Trump, experts wonder what doors a law like this could open to other states creating qualifications for presidential candidates to be on the ballot. The National Conference of State Legislatures tracks 17 other states that have considered tax return qualifications this year for getting on their primary ballots, according to the Associated Press.

“We could see a birth certificate requirement in an Obama-like situation,” theorized Rick Hasen, an election law expert at the University of California at Irvine and with the Election Law Blog.

Liron Lavi, a research fellow at UCLA who focuses on elections and democracy, said this law is problematic, in a democratic sense, because it is so overtly political. Responding to Trump’s policies by, say, making your city or state a sanctuary for undocumented immigrants is one thing. Responding to Trump’s electoral chances is another.

“It is directly aimed at a candidate, at Trump, rather than toward policies and values,” she said.

But there’s a real chance Trump could win these lawsuits, be on the ballot in California and keep his tax returns secret.

Trump’s team is arguing that the California law is unconstitutional on grounds that it violates the constitutionally mandated definition of who can be president.

The Constitution purposefully limited the restrictions on who can be president to these questions: Are you 35, and have you lived in the United States for at least 14 years? Trump’s campaign argues that California is putting another layer on top of that: Have you released your tax returns?

For the past 40 years, presidential candidates releasing their tax returns has been tradition, not law. It’s an option, one Trump chose not to take. “The issue of whether the president should release his federal tax returns was litigated in the 2016 election and the American people spoke,” Sekulow said in his statement. (Though Trump actually campaigned that his tax returns were being audited and he would release them when they were done.)

Hasen was not making any predictions, but he pointed out there are at least two cases where the courts have been circumspect about states’ authority to limit who is on the ballot — one in which the Supreme Court said states cannot impose restrictions on candidates for Congress.

Still, each state conducts its own presidential primary, and he said courts tend to give broader leeway for how states set their own rules for presidential candidates and elections.

Congress is currently suing the Internal Revenue Service to get 10 years’ worth of Trump’s tax returns. New York passed a law allowing Congress to request Trump’s state tax returns. But it’s California that has come closest of all to forcing Trump to release his returns. The legal showdown over this is going to be very revealing about whether Trump’s tax returns will ever be public.