Senator Richard Blumenthal, the top Democrat on the Senate Permanent Subcommittee on Investigations, sent a letter Thursday to Cantor Fitzgerald CEO Brandon Lutnick demanding details on the firm's relationship with Tether, the issuer of USDT and the largest stablecoin operator globally.

The letter escalates Blumenthal's scrutiny of Tether's role in illicit finance and puts Cantor Fitzgerald — the custodian and manager of Tether's U.S. reserves — directly in the subcommittee's crosshairs. Brandon Lutnick took over as CEO when his father, Howard Lutnick, left the firm to become President Donald Trump's Secretary of Commerce, a transition the Connecticut senator also asks about in the letter.

Blumenthal wrote: "Just as Tether has made untold millions in interest and investments from the stablecoins used in these illicit activities, so has Cantor Fitzgerald profited from its relationship with Tether." He pressed the younger Lutnick on his company's banking and sanctions safeguards and on his father's history with Tether at the firm.

The senator also challenged Tether's offshore posture. "While Tether claims to operate out of El Salvador, the vast majority of its assets reside in the United States under your custodianship," Blumenthal wrote. "As Congress considers how to best regulate digital assets, your partnership with Tether will provide important insights into the inner workings of this industry."

What does the letter request?

The letter contains a series of pointed requests, including:

• A full description of "all steps Cantor Fitzgerald has taken to investigate allegations that Tether's stablecoin has been used in illicit finance and money laundering, including within Iran's shadow banking network and for purposes of Russia sanctions evasion."
• Details of Cantor's banking and sanctions compliance controls.
• Information on Howard Lutnick's dealings with Tether during his tenure leading the firm.

Neither Cantor Fitzgerald nor Tether immediately responded to requests for comment sent to their spokespeople.

Why does committee control matter?

The probe lands as congressional leverage shifts. Blumenthal and fellow crypto critics such as Senator Elizabeth Warren have operated with limited authority as members of the Senate minority. A Democratic majority in the next Congress would change that calculus: winning several more seats could place them atop committees with subpoena power to legally compel documents and testimony.

Prediction markets currently favor that outcome. Kalshi prices a Democratic Senate takeover at 61% and Polymarket at 64%, up from near 50-50 several weeks ago. Both platforms put the probability of Democrats retaking the U.S. House of Representatives above 90%.

What are the operational stakes?

Cantor Fitzgerald occupies a structurally critical position in the stablecoin market. The firm holds and manages Tether's reserves on U.S. soil, and the two companies share additional business interests beyond custody. Any compelled disclosure of custody arrangements, reserve composition or compliance procedures would surface operational detail that Tether has historically kept private.

The inquiry also touches the Trump administration directly. Howard Lutnick's move from Cantor's leadership to the Commerce Department placed a top Tether business partner inside the cabinet, and Blumenthal's letter signals Democrats intend to examine that intersection should they gain gavels.

With the November election approaching and prediction markets pricing a likely chamber flip, Cantor Fitzgerald and Tether face a narrowing window before congressional investigators could gain the subpoena authority needed to force answers on USDT's U.S. reserve operations.