For years, Cory Booker has bashed Donald Trump over his failure to publicly release his income tax returns, something every U.S. president had done for the previous 40 years. But with tax season now underway, Booker is yet to release his own returns, even as several of his fellow Democratic candidates have already done so.

That may be about to change.

Trump trying to explain why he's the only pres candidate in decades not to release his tax returns and is FAILING miserably #debatenight — Cory Booker (@CoryBooker) September 27, 2016

“Cory believes that anyone who wants to run for president should release their tax returns," said Sabrina Singh, the Booker campaign’s national press secretary. "Unlike Donald Trump, Cory plans on releasing his tax returns.”

Still, it’s not yet clear when Booker’s returns will be released. Singh declined to offer a timetable.

Waiting isn’t likely an option. On Monday, U.S. Sen. Amy Klobuchar, D-Minn., released a dozen years worth of returns, just days after Washington Gov. Jay Inslee, and U.S. Sen. Kirsten Gillibrand of New York, both Democratic candidates for president in 2020, did the same.

Last August, U.S. Sen. Elizabeth Warren of Massachusetts had released a decade’s worth of her own tax returns, posting them online.

It’s been a month since U.S. Sen. Bernie Sanders pledged to release a decade’s worth of tax returns at a town hall meeting, and he’s now facing increasing scrutiny for not making good on his pledge.

Booker has only ever offered a brief glance at his returns: When running for U.S. Senate in a special election in 2013, his returns were shown to just a handful of reporters, but could not be photographed or copied. He also allowed his 2014 returns to be examined in the same restrictive fashion.

The returns revealed a near-monastic lifestyle. While he earned more than half a million dollars in 2013, much of it from speaking fees, Booker donated most of it -- $440,000 in cash, property and stock -- to charity, according to the tax returns.

Democrats in the Legislature will later this year to advance a bill that would compel any candidate for president -- regardless of party -- to release their tax returns if they hoped to be on New Jersey’s ballot.

“This isn’t aimed at any specific individual but it has its roots in the traditional of candidates of major parties making their tax returns available to assist in the voting process,” said Assemblyman John McKeon, D-Essex, its prime sponsor. “When Trump broke that tradition, it became necessary to create a law so that it’s no longer an option to hide your (tax) returns.”

Since 2015, Trump has insisted that his personal tax returns cannot be released because he is in the midst of an ongoing IRS audit.

Claude Brodesser-Akner may be reached at cbrodesser@njadvancemedia.com. Follow him on Twitter @ClaudeBrodesser. Find NJ.com on Facebook.

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