President Trump has said that Americans "don't care at all" about his tax returns, which he has refused to publicly release, bucking a 40-year tradition observed by U.S. presidents and presidential nominees.

Turns out though, many people do care.

Polls show 74% of Americans say he should release them. Many lawmakers, including some Republicans, have publicly called on him to do so. Constituents have pressured their representatives at town halls to make it happen. And to date, there are more than 1 million signatures on a White House petition demanding that the president release his returns.

Now protesters are planning nationwide marches to demand the same on April 15.

So far, there are 135 marches scheduled across 40 states and the District of Columbia.

Several of the marches will be led by a symbol of cowardice: A big, blow-up chicken, according to Delvone Michael, a senior political strategist for the National Working Families Party and a member of The Tax March executive committee that is organizing the April 15 marches.

Related: Democrats aren't giving up on Trump's tax returns

Based on the principles posted by the organizers, the main message seems to be this: You work for the people, Mr. President. And we are demanding that you release your returns so we can better see where you may have financial conflicts of interest and foreign entanglements.

"Without his tax returns, we're in the dark ... about whether he's operating on behalf of himself or all Americans," Michael said.

It's impossible to gauge how many -- or how few -- people will show up on April 15. Based on the numbers of those who indicated on Facebook that they'll attend, the biggest cities (e.g., Washington, D.C., Los Angeles, New York, Philadelphia, Chicago and Boston) will draw the biggest crowds with anywhere from 4,000 marchers to more than 20,000.

Many of the events, however, may draw fewer than 100 people. Take the planned march in Cheyenne, Wyoming. Right now its Facebook page indicates just 49 people say they'll go, and a total of 84 say they're "interested."

Related: Republicans face tough questions about Trump's tax returns at town halls

But the tax marches may surprise on the upside. Kathleen Petersen, a retiree who is organizing the Cheyenne march, also helped organize the local Women's March there the day after Trump was inaugurated.

"We thought we'd be lucky if we got 200 people. And we got 2,000," Petersen said.

The Cheyenne event will take place on a main road in front of the city's IRS building. "It's important to have this march to say we do care," Petersen said.

And yes, there will be a big blow-up chicken on site.

Trump is under no legal obligation to release his tax returns. He has said he would when they're no longer under audit, even though an audit doesn't preclude him from releasing them if he chooses.

His 2016 tax return, however, likely isn't under audit yet. When asked by a reporter last week whether Trump might release his latest return by April 15, White House Press Secretary Sean Spicer said, "I don't know."