By Peter Nicholas and Josh Zumbrun
PALM BEACH, Fla. -- Giving no ground, President Donald Trump dismissed Saturday protests calling for him to disclose his tax returns as the work of political opponents unhappy about his election victory.
"Someone should look into who paid for the small organized rallies yesterday," Mr. Trump tweeted Sunday morning. "The election is over!"
With Americans' tax returns due to the Internal Revenue Services on Tuesday, in Washington, D.C., Palm Beach, Detroit and other cities across the country, demonstrators joined in street protests demanding that Mr. Trump follow the practice of past presidents over the last four decades and make public his tax returns. Doing so would help reassure the public that Mr. Trump is avoiding financial conflicts of interest that could arise given his real estate holdings and far-flung business interests, some involved in the demonstrations said. In his tweets, Mr. Trump suggested the protesters were motivated by something other than a desire for transparency and ethics in government.
"I did what was an almost impossible thing to do for a Republican -- easily won the Electoral College!" he wrote in another tweet. "Now Tax Returns are brought up again?"
Those who want Mr. Trump to show his tax returns are looking to pressure him on different fronts: legal, political and legislative. Sen. Chuck Schumer of New York, the Senate Democratic leader, suggested on Friday that Congress might use Mr. Trump's desire to overhaul the tax code to pressure him release the tax records.
"Until President Trump releases his full tax returns, a cloud of suspicion will remain and make it much more difficult to get tax reform legislation through the Congress," Mr. Schumer said.
By the late 1970s it was common practice for presidential candidates to release their tax returns, though they have released records for differing time periods and at different stages of the campaign. Beginning with Jimmy Carter, every president has released their returns while in office. A 1978 ethics law requires officeholders, including the president, to disclose their assets and sources of income. The figures can be reported in broad ranges and the law doesn't mandate the release of tax returns.
Since Mr. Trump has taken office, House Democrats have tried unsuccessfully to pass measures compelling the release of the president's returns. Last week, a public interest group called the Electronic Privacy Information Center filed suit against the IRS demanding release of Mr. Trump's returns, and more than one million people have used a petition tool on the White House website to call for Mr. Trump's "full tax returns."
A day after the street demonstrations, organizers dismissed Mr. Trump's unsubstantiated claim that protesters were paid.
"As much as I'd love to have had some support from shadowy imaginary billionaires, that's not what happened," said Gwen Snyder, director of Philadelphia Jobs with Justice and the organizer of the Philadelphia march on Saturday, said. "I work for a tiny community organization that's grass roots funded. We didn't have a budget for the tax march. Our money was coming in $5 and $10 and $20 increments from people who wanted the march to succeed."
In an interview, Rep. Jamie Raskin, a Maryland Democrat who took part in the protest in Washington, issued a challenge to Mr. Trump.
"I'm sure the organizers of the march would gladly reveal all of their financial backers if the president would release his tax returns," Mr. Raskin said.
Over time, Mr. Trump and his advisers have advanced different reasons for why Mr. Trump has declined to release his tax records. Mr. Trump has cited a continuing IRS audit as the driving issue. In an interview she gave in January, counselor to the president Kellyanne Conway said: "We litigated this all through the election. People didn't care."
With Tax Day approaching, White House Press Secretary Sean Spicer was asked at a press briefing last week when Mr. Trump would release records covering 2016. Mr. Spicer said the president has "been under audit." He added that "this question has been asked and answered over and over again," going on to say that Americans are more focused on actions that would create jobs and improve the economy.
In a Bloomberg/Morning Consult poll released last week, 53% of voters surveyed said they believed Mr. Trump should be required to release his tax returns, compared with 32% who said he should not be compelled to do so.
With Mr. Trump spending the weekend at his Mar-a-Lago resort in Florida, the protesters took pains to get his attention.
As Mr. Trump returned from a golf outing Saturday in West Palm Beach, his motorcade took a longer route that avoided protesters gathered along a main thoroughfare to Mar-a-Lago, according to press pool reports.
"Pay your taxes," people yelled as they headed toward a demonstration near the president's resort.
Write to Peter Nicholas at firstname.lastname@example.org and Josh Zumbrun at Josh.Zumbrun@wsj.com