Sen. Chuck Grassley stepped up pressure in his probe of Hillary Clinton’s private email network last week, blocking the nominations of high-level State Department nominees and blasting Democrats for misrepresenting the identity of his confidential source.

The Iowa Republican, who chairs the Senate Judiciary Committee, turned the investigation’s focus to Heather Samuelson, a former campaign aide who was given unfettered access to Clinton’s emails before the State Department ever saw the documents.