Representative Adam Schiff, the lead House impeachment manager, accused the National Security Agency on Sunday of withholding intelligence that might be useful in the trial.

Republicans called such complaints proof that the case against Mr. Trump was so weak that Democrats were scrambling to bolster it. Over the weekend, the president’s legal team denied that he had committed impeachable acts and denounced the charges against him as “brazen and unlawful.”

Background: President Bill Clinton’s impeachment trial 21 years ago is serving as a template for Mr. Trump’s. It will include some of the same faces (hello, Ken Starr), but there are distinct differences.

Related: News outlets, including the normally sedate C-SPAN, are up in arms about new restrictions on their movement inside the Capitol, which they say will prevent them from easily interviewing lawmakers about the trial.