WASHINGTON — Pursuing a return to public service came at a cost to Hillary and Bill Clinton, as their considerable joint income dropped by nearly two-thirds last year when the former secretary of state began her run for president.

The Clintons released their most recent tax filing Friday, as well as 10 years of tax documents from running mate Tim Kaine and his wife, part of a renewed call for Republican nominee Donald Trump to do the same.

For more than a year, both Republicans and Democrats have pushed the billionaire real estate magnate to back up his boasts about business acumen and charitable giving by publicly disclosing federal and state tax filings, a customary gesture of transparency for presidential aspirants and one his rivals were confident could offer political ammunition.

“Donald Trump is hiding behind fake excuses and backtracking on his previous promises to release his tax returns,” Clinton campaign spokeswoman Jennifer Palmieri said in a statement. “He has failed to provide the public with the most basic financial information disclosed by every major candidate in the last 40 years. What is he trying to hide?”

But Clinton’s gesture was not without risk. It invited a fresh look at the sources of income for the candidate and the former president, which have invited political attacks before, particularly the seven-figure speaking fees both attracted.

Hillary Clinton, who announced her candidacy in April 2015, made $1.48 million from speaking engagements in 2015, a sharp decrease from the nearly $10.5 million she generated the year before. Former President Clinton made $5.25 million in speaking fees in 2015, less than half of his earnings the previous year.

The couple also generated income from book sales and Bill Clinton’s consulting business. Both listed the same occupation on returns signed in March: “speaking and writing.”

Together they reported an adjusted gross income of $10.6 million in 2015, down from nearly $28 million the year before. Their combined payments in federal, state and local taxes amounted to an effective tax rate of 43.2 percent, the sixth time in 15 years it has exceeded 40 percent.

In an economic speech Thursday, before this reminder of her family’s wealth, Clinton sought to emphasize her more humble roots, calling herself “the product of the American middle class.”

“My dad was able to go to college, and eventually start his own small business, and then send me out into the world to follow my dreams,” she said. “No matter how far those dreams have taken me, I have always remembered, I’m the daughter of a small-business owner and the granddaughter of a factory worker — and proud of both.”

By comparison, the Kaines’ joint adjusted gross income was a far more modest $313,441, reflecting the vice presidential nominee’s income as a U.S. senator and his wife’s as Virginia’s secretary of education.

The average payout for a single Clinton speaking engagement exceeded the $174,000 annual Senate salary of her running mate.

The Clintons made a combined $153 million from 729 paid speeches from 2001 to May of 2015, a CNN analysis found this year. With the latest release, the Clintons have disclosed nearly four decades of tax returns, dating to Bill Clinton’s first year as attorney general of Arkansas.

The Trump campaign charged that Clinton has “turned over only the records nobody wants to see from her.” Instead of tax documents, said Trump spokesman Jason Miller in a statement, Americans want to see the 33,000 emails deleted from Clinton’s private server, transcripts of her paid speeches to firms with Wall Street ties and other documents from the Clinton Foundation.

“Hillary Clinton is at the center of an international corruption scandal that reveals her use of government authority and influence for personal gain,” Miller said. His statement did not address Trump’s tax returns.

Vermont Sen. Bernie Sanders repeatedly called for Clinton to release the speech transcripts during the Democratic presidential primaries. Clinton in turn called for Sanders to release years of tax returns, something he eventually did for 2014.

Candidates’ disclosure, or lack thereof, of tax returns has been a staple of presidential campaigns. In 2012, the top Senate Democrat, Harry Reid of Nevada, helped build pressure on Republican nominee Mitt Romney to release his returns by openly suggesting he had paid no taxes at all. Romney eventually released a single year’s filing and a summary of taxes paid for two decades.

This year, while not a candidate himself, Romney demanded that Trump provide similar disclosure as part of an ultimately unsuccessful campaign to discredit the GOP front-runner during the primaries.

Romney’s comments — saying the disclosure would show whether Trump was the “real deal or a phony” — were included in a Web video by the Clinton campaign Friday morning that includes similar attacks from his GOP rivals.

Trump has said he can’t release his tax returns because they are under audit by the Internal Revenue Service, an explanation he repeated Thursday in an interview on Fox News.

“You don’t learn very much,” he said. “I have been under audit now for, I think, 15 years straight, which is ridiculous because other people don’t get audited.”

No law or rule prevents Trump from releasing tax information while under audit, according to the IRS, though tax experts have cautioned against releasing information from the years under audit.

Democrats in particular have raised questions about whether Trump’s filings might reveal connections between Trump’s business empire and Russian interests.

Appearing alongside Clinton at a recent campaign event in Nebraska, investor Warren Buffett, one of the world’s richest men, noted that he, too, was under audit but nonetheless issued a challenge to Trump.

“I would be delighted to meet him anyplace, anytime between now and Election Day. I’ll bring my tax return; he can bring his,” Buffett said.

“You will learn a whole lot more about Donald Trump if he releases his tax return,” he added.