(Win McNamee/Getty Images)

As a candidate for Congress, Paul Ryan has released financial disclosure forms for years, but he has never released his tax returns.

We know that Ryan turned over "several years" of tax returns to the Romney campaign during the vice presidential vetting process. We have asked the Romney campaign if any of those returns will be made public. No answer yet.

As a reminder: Dick Cheney released 10 years of returns after he was named George W. Bush's running mate in 2000. Sarah Palin released two years when she added to the John McCain ticket in 2008.

The level of disclosure for the vice presidential candidate is normally set by the presidential candidate. Cheney recently told ABC News that Romney has released enough tax returns. But he also explained why he released a decade of his own as a running mate.

"I did what [Bush] did. In other words, you weren't going to have the presidential candidate do 10 years and the vice-presidential candidate not do that," he said.

An assessment of Ryan's congressional financial disclosures by the Los Angeles Times pegs his wealth at between $2 million and $7.7 million with income from his congressional salary and an inherited trust in the name of his wife.

Democrats have criticized Mitt Romney for not releasing more than one year of tax returns . Romney has also released preliminary returns for 2011. He has promised to release the final return when it is completed.

The Obama campaign and other Democrats have argued that Romney should release more years of his returns, like President Obama did as a candidate. But Romney has said he will not; Democrats, he said, will never be satisfied with how many years he releases and just want to use the information to highlight Romney's wealth.

"If he had two years out, they'd want four," Cheney told me, defending Romney. "If he had four years out, they'd want six. If he had six years out, they'd want 10. He's made his judgment. I'm confident - I have great confidence in what he's put out there. He's been a very successful man. And there's no evidence of any kind that he's done anything improper or inappropriate."

Get more pure politics at ABC News.com/Politics and a lighter take on the news at OTUSNews.com

As a vice presidential candidate, then-Sen. Joe Biden released 10 years of tax returns in September 2008 following the Democratic National Convention. He has released his returns every year since.

Candidate Barack Obama released eight years of tax returns before the election: seven years' worth in March 2008, and his '07 return in April 2008. He has released his returns every year since.