US Senator Richard Blumenthal of Connecticut sent a letter to Tether on Thursday requesting documents related to any contracts, payments, communications and lobbying between the stablecoin issuer and Nxum, the firm co-founded by Hines. The request stems from a Wall Street Journal report that Tether had a $6.3 million deal with Nxum.
Blumenthal said the probe was part of what he called the Trump administration's “self-enrichment and self-dealings with cryptocurrency firms.” He stated that Hines failed to divest his one-third stake in Nxum and instead used encrypted messaging applications to coordinate with the company on lobbying, advocacy and “browbeating of members of Congress that were opposed to, or had sought changes to, pending stablecoin legislation.”
The lawmaker added that the “highly unusual terms and nature of Tether’s business relationship with both Nxum and Bo Hines raise alarming ethical and legal concerns, indicating that Tether was likely well aware of the illegality and impropriety of issuing payments to a current White House official with such a direct role in shaping cryptocurrency legislation that was instrumental to its business.”
Hines served as executive director of the President’s Council of Advisers on Digital Assets from January to August 2025, when he left the White House to join Tether as a strategic adviser. He later became CEO of Tether US. Another former White House crypto adviser, Harry Jung, left his position in July 2026 and joined Nxum as a managing director in August.
Tether did not immediately respond to a request for comment.
The investigation comes as prediction markets favour Democrats retaking control of both chambers of Congress in the 2026 midterm elections, which would give Blumenthal and other Democrats greater authority to investigate ties between the Trump administration and the crypto industry. Election Day is 3 November.