Evan McMorris-Santoro September 22, 2011, 1:38 PM

Republicans on Capitol Hill have found a new hidden document conspiracy to push to now that President Obama’s long-form birth certificate is a matter of public record. Warren Buffett, they demand, show us the tax return!

The Hill reports big names in Congress are starting to say Buffett “needs to reveal his finances if his views on tax rates are going to serve as the basis for Obama administration policy.”

NRSC chair John Cornyn (TX), who took the call to Twitter Thursday, explained to ABC News that knowing how Buffett makes his money could change the way people view the so-called “Buffett Rule” that President Obama is making a cornerstone of his call for increased taxes on the super-rich.

“If he’s going to be the gold standard, so to speak, in terms of what our tax policy should be, let’s look at them,” Cornyn told Jonathan Karl.

Politico transcribed some more from the interview:

I know that Mr. Buffett’s not likely to release his tax records but I’ll bet what it’ll show you is that most of what he earns is from capital gains, which is taxed at a 15 percent tax rate rather than deriving it as income [for] which he’d pay a much higher tax rate,” Cornyn said. “If he doesn’t derive ordinary income and if all of his, what he puts in his pocket is based on capital gains, I think that would be an important information.

He’s not the only one. Tea Party favorite Sen. Jim DeMint (R-SC) is also sniffing around for the tax records of one of America’s most successful investors (and one of Obama’s most prominent supporters.)

“I’d love to see Buffett’s tax returns so we can see what he’s really doing, because he’s kind of operating in the dark here, making some claims,” DeMint told Bloomberg, as snagged by The Hill.

“If he’s paying taxes on capital gains, taxes have been paid by the corporations before they gave it to him,” DeMint said. “He may not be paying it personally, but the tax is being paid at a higher rate than his secretary’s making.”

And that seems to be the goal here — to tear down the claim that Buffett pays a lower rate than his secretary. The anecdote is a favorite of supporters of Obama’s new taxes on the rich, and has already prompted some rebukes.

Freshman Rep. Tim Huelskamp (R-KS) — last seen taking a drubbing on basic economics from the CBO — made the Buffett birther call official in a open letter to Buffett today, The Hill reports. “Given the use of your name and your story as the guiding force for the President’s policy prescription, it is my hope that the evidence to justify such a change in policy will soon be available for public review,” he wrote in the letter.

Here’s some video of DeMint getting his Buffett Birther on:

Deficit, Jim DeMint, John Cornyn, Republicans, Taxes, Tim Huelskamp, Warren Buffett