Parnas, flanked by his attorney Joseph Bondy and others, made his way from Union Station to the Capitol while walking among a throng of reporters.

It's unclear where Parnas will be watching the proceedings from, as a federal judge on Tuesday denied his request to have his GPS device removed, thereby quashing his request to attend the trial because Senate rules do not permit any electronic devices in the gallery.

Asked whether anything specific would be submitted by them to lawmakers during Wednesday's proceedings, Parnas and Bondy said they didn't plan to do so. The purpose of their presence, they said, was to "watch (a) momentous event."

Parnas told CNN his goal is "to look at these senators and have them look at me and see we need to call witnesses ... me and (former national security adviser) John Bolton ... the two of us put all the dots together."

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