While states generally have purview over elections, such a provision would definitely be challenged in federal court.
Via The Hill:
Washington’s state Senate passed a bill this week that would drop President Trump from the state’s 2020 presidential ballot until he releases his tax returns.
The bill, which advanced Tuesday to the state’s House of Representatives, according to CBS News, would require any candidate on the ballot for president in the state to release five years of tax returns before appearing in a general or primary election.
Senators voted by a 28-21 margin to approve the bill, according to CBS. The state’s attorney general and solicitor told lawmakers in a letter this week that the proposal likely was constitutional, but analysts expect the law if passed to be challenged in federal court.
“The disclosure requirement you propose is likely Constitutional,” the two wrote to lawmakers, according to CBS, adding that the measure “would definitely be challenged in court.”
Democrats who supported the bill said the provision was necessary to force a return to norms surrounding the release of presidential candidates’ tax returns. “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 Sen. Patty Kuderer (D), who sponsored the bill, according to CBS.