Washington Gov. Jay Inslee, a Democrat running for president, supports a bill that would remove President Trump from the state’s ballot in 2020 if he does not release his tax returns.

Tara Lee, Inslee’s deputy communications director, confirmed to MSNBC the governor is “supportive of this bill." The legislation, which passed the state Senate earlier this month, would require all presidential candidates and their running mates to release their tax returns from the last five years in order to appear on the state’s ballot in any primary or general election.

NEW: Washington Gov. and 2020 candidate @GovInslee confirms to @AriMelber that he is backing a state bill that if passed would kick Trump off the ballot in his own state unless he releases his tax returns pic.twitter.com/gpDVdVoSLq — TheBeat w/Ari Melber (@TheBeatWithAri) March 18, 2019

Trump refused to release his tax returns during the 2016 election, citing an IRS audit as the reason.

The legislation still needs to pass Washington’s House of Representatives before reaching Inslee's desk, but state Sen. Patty Kuderer believes Inslee’s support will aid its passage in the lower chamber.

“I'm very happy about it,” Kuderer, a Democrat who sponsored the bill, told MSNBC on Monday. “It will make it easier to get it through the House, so it's good news.”

Republicans are concerned the measure would spark a costly legal battle. "We're on really risky ground when we're trying to place conditions on a federal election," Washington state Sen. Hans Zeiger, a Republican, told CBS News.

Washington Attorney General Bob Ferguson and solicitor general Noah Purcell said they believe the proposal is legal, but they warned lawmakers it "would definitely be challenged in court."

Inslee announced earlier this month that he would run for president in 2020.