Donald Trump may be denying a conflict of interest between his sprawling private business and his job as president-elect, but Sen. Elizabeth Warren has some questions.

In a letter released today, cosigned by Rep. Elijah Cummings, the Massachusetts senator urged federal regulators to investigate if Trump was already using his public position for private gain.

We have already learned that Trump took a break from presidential transition meetings to meet with his private Indian business partners, that he reportedly asked in his first call with Argentina’s president about a business permit for a real estate deal (the claim was denied), and that his daughter sat in with meetings with the Japanese prime minister. (Ivanka Trump is supposed to be the head of the “blind trust” separating Donald Trump’s personal and private affairs.)

But there’s also so much we simply don’t know yet. And Warren and Cummings want the federal government to find out — as soon as possible.

They ask:

To what extent have Mr. Trump's conflicts of interest affected his presidential transition? What is the impact and potential impact of his refusal to set up a qualified blind trust to prevent conflicts of interest? Has Mr. Trump conducted Trump Organization business during the transition? Is there transparency with regard to his activity with his business interests? Have his conflicts potentially affected the policy positions of his new Administration? Have his family members maintained appropriate distance between the business of the Trump Organization and the presidential transition? Has the Trump transition used taxpayer dollars efficiently and effectively? Have funds from the transition or associated with the transition (such as reimbursements from the Secret Service) gone to companies owned by Mr. Trump? If so, how much was the total amount paid to Mr. Trump's business entities? Have the payments been fair and reasonable?

The pretext of this letter is to ask the Government Accountability Office to figure out how Trump is using the $9.5 million that helps pay for his team during the presidential transition process. (Every time the presidency changes hands, the government allocates millions of dollars to help oversee the shift.)

“We have significant questions about the extent to which Mr. Trump's conflicts of interest and other problems [that] are affecting his transition are compromising the use of taxpayer funds,” they write.

This is a preview of the coming fight ahead

Trump may be already using federal money for his own ends, based on what we’ve seen from his campaign. Warren and Cummings note, for instance, that nobody has any idea how much Trump is spending to fly on his private plane between New York City and Washington, DC.

But while the letter is written ostensibly to call for an investigation of this interim transition period, it’s really just a preview for the larger looming fight ahead.

Trump, of course, will soon not just command the financial resources offered for his transition team. He will have discretion over a vast federal bureaucracy, with the ability to spend infinitely more resources, bolster his sprawling private companies in places from Saudi Arabia to Argentina to China, and stretch constitutional limits around receiving gifts from foreign governments.

As New York magazine’s Eric Levitz has noted, there’s no real way for congressional Democrats to stop Donald Trump from seeking private profit from his interactions with foreign governments. But starting to call attention to it now — and build public pressure against it — seems like a natural first step.

Here’s the full text of the letter from Warren and Cummings:

Watch: It’s on America’s institutions to check Trump