Federal Register
The cleanest way to verify executive orders, proclamations, rule changes, and agency notices. If they changed federal policy, the paper trail usually starts here.
Congress.gov
Bill text, amendments, sponsors, floor actions, and status. Good for killing fake summaries of legislation before they spread.
White House statements
Official spin, yes. But also an admissible record of what they wanted on the record at a given moment. Useful when the rewrite comes later.
C-SPAN + full transcripts
For speeches, interviews, hearings, and floor remarks, video and transcripts beat selective clips every time.