Ted Cruz and Marco Rubio are upping the ante in their ongoing attempt to force Republican presidential front-runner Donald Trump into releasing recent statements from his tax filings.

Both 2016 GOP candidates have released summary pages from their own filings and are hoping their actions will propel Trump into following suit.

Despite repeated vows to release his tax records, Trump has thus far kept them under lock and keep. He now insists that won't change until the IRS completes an audit of his returns.

"We're putting these out today to put pressure on Trump and the other candidates to release theirs," said Rubio campaign spokesman Alex Conant.

Cruz Speculates About Trump's Taxes

Meanwhile, Cruz went as far as to speculate there might be "a number of bombshells" in the billionaire real estate mogul's returns. Cruz further speculated that possibilities could range from "exaggerations about the celebrity businessman's earnings to significant contributions to Planned Parenthood."

On Sunday, during an appearance on ABC's "This Week," Cruz tried raising the stakes even more by adding, "There have been multiple media reports about Donald's business dealings with the mob, with the Mafia. Now maybe his tax returns show that those business dealings are a lot more extensive than has been reported."

So far, both Cruz and Rubio have only made the first two pages of their filings to IRS publicly available, which leave out such intimate details as actual tax deductions. Both have hinted they are willing to release more, provided all the other candidates do likewise.

"If Marco wants to release the complete thing for the recent years, I'm happy to do so as well," Cruz said. He added he views Trump's unrelenting delay "unprecedented in presidential politics."

Since taking office in the Nation's Capital, Rubio's filings show he has earned from $276,059 to $938,963 annually, and he has paid between $46,500 and $254,894 in federal income tax. Most of his income stems from a business that collected royalties on two books: Rubio's memoir, "An American Son," and a pre-campaign tract, "American Dreams."

Rubio's tax rate on Released Docs Tops out at 31 Percent

Rubio paid an effective tax rate of just over 31 percent in 2012, his most lucrative year. But by 2014, the family's income dropped to $335,963, resulting in him and his wife paying a tax rate of 24 percent.

Cruz released returns from the years 2011 through 2014. They show him and his wife Heidi brought in an annual average of $1,131,792, with large portions of their income coming from Cruz's work in 2011 and 2012 at the law firm Morgan, Lewis and Bockius, and his wife's work at Goldman Sachs.

In all, the couple reported earnings of $5.2 million over those years and paid an average effective tax rate of 37.6 percent.