President Trump listens during a news conference in the East Room of the White House on Wednesday. Thousands are expected during a Saturday rally in the District urging Trump to release his tax returns. (Jabin Botsford/The Washington Post)

An idea that sprung from a law professor’s tweet after President Trump’s inauguration will unfold Saturday on the Mall, where thousands of protesters plan to call on Trump to release his personal tax returns. The demonstration is expected to be the largest of more than 100 affiliated protests planned across the country.

The Tax March, which falls on the nation’s traditional April 15 deadline to file taxes, is expected to be one of the most high-profile demonstrations of the Trump era since protesters around the world participated in women’s marches — marches that served as an unprecedented rebuke to Trump’s presidency on his first full day in office. Presidents are not required to release their tax returns but have done so voluntarily dating to the 1970s.

Jennifer Taub, a law professor specializing in business at Vermont Law School, said that after she attended a Women’s March protest on Jan. 21 in Boston, she felt optimistic about the power of organized resistance. It spurred her to action the next day when she heard counselor to the president Kellyanne Conway say on national television that Trump wouldn’t release his tax returns because people don’t care.

Taub tweeted that the nation should plan a march on Tax Day to show the White House that the public does care. At the same time, comedian Frank Lesser made a similar plea on Twitter. The tweets caught on, and now Taub and Lesser are co-founders of the march, which has garnered the support of nearly 70 progressive organizations.

[Trump won’t release his tax returns because people don’t care, top adviser says]

Jennifer Taub, a law professor at Vermont Law School, helped found the Tax Day march after being inspired by a Women’s March protest in Boston in January. (Ilana Panich-Linsman)

“I do care about his taxes. I care about transparency and conflict of interest,” Taub said. “I think it’s important for us, we the people, to express First Amendment rights and say we want to see them.”

Trump has refused to release his tax returns, stating that he has been under audit. Asked for comment Thursday on the Tax March, the White House referred to comments earlier this week from press secretary Sean Spicer, who repeated that Trump is under an IRS audit, but indicated the president has been transparent with his finances.

“We filed our financial disclosure forms the other day in a way that allows everyone to understand,” Spicer said at a Tuesday news briefing.

Marchers in Washington are expected to be joined by those in more than 100 other cities across the country and around the world, including New Orleans, San Antonio, Nashville and London, organizers say.

In Washington, organizers have worked with government agencies, including D.C. police and the National Park Service, to obtain permits. The Park Service permit indicates that organizers expect up to 10,000 people.

Mike Litterst, a spokesman for the Park Service, said the Tax March and the Science March the following weekend are among the largest protests the agency is expecting this spring in Washington.

[Women’s marches: More than one million protesters vow to resist President Trump]

(Gillian Brockell/The Washington Post)

The Tax March will begin at noon Saturday on the west lawn in front of the Capitol, with a lineup of speakers that includes Sen. Ron Wyden (D-Ore.), Rep. Maxine Waters (D-Calif.) and Rep. Jamie B. Raskin (D-Md.).

From there, protesters will march west along Pennsylvania Avenue NW before ending near the Lincoln Memorial. The event is expected to end about 4 p.m.

In an interview, Raskin referred to polls during the presidential campaign that showed a majority of Americans — and a majority of Republicans — believed that Trump should release his tax returns. Raskin said Congress couldn’t have meaningful conversations about a tax revamp without knowing whether proposed tax laws would be a financial boon to Trump and his businesses.

“This is going to be an old-fashioned tax protest calling for King Donald to release his taxes,” Raskin said. “The reason why this is such a big deal is that, whether you like it or not, Donald Trump is a role model for the rest of the country. Donald Trump has made it clear that he will try to get away with whatever he can and then try to fight it out in court. If the rest of the country acted the way he did, the tax system would fall apart.”

Taub said she doesn’t expect the president to release his tax returns as a result of the march, but she said its impact might be felt in other ways, such as compelling state legislatures to pass laws calling for more financial transparency from elected officials. New laws on the state or federal level, she said, could eventually force Trump and future presidents to release their returns.

Taub said organizers also hope Congress will feel pressure from constituents to pass tax laws that benefit more than just the richest Americans.

“One way or another, we will see his tax returns, I believe,” Taub said.