"This raises questions regarding political intelligence brokers' ability to gather information from [the Medicare agency] in order to predict market moving events."
Grassley, who is the top Republican on the Senate Judiciary Committee, asked Tavenner for the names of everyone who learned of the Medicare Advantage decision in advance.
He also asked for a timeline of how the decision was made, and copies of all related communications.
The letter set a deadline of April 9, when Tavenner is scheduled to appear before the Senate Finance Committee regarding her nomination to be permanent head of the Centers for Medicare and Medicaid Services.
Grassley wrote to Tavenner on the same day that government auditors released a major report about political intelligence and the challenge of making it more transparent.