I do this all the time for other people. Daily almost.
My scenario would be that the creator or presenter made a copy of the program and copied it to a CD. The CD would allow the presenter to make last minute changes and fine tune the presentation (it's got to be perfect don't you know) or maybe we're we're still waiting for some final figures from one of the other presenters.In any case the actual PowerPoint is not on the harddrive.
Most people at this level tend to be perfectionist and want to have a backup copy in case something goes wrong with the original at Showtime.
When professional people go to a hotel there is often an AV staff that set up the equipment and get it ready for the presentation.
There's your weak link. Many really smart people are one, either "gizmo challenged" and two, have only supervised the creation of the disc and not actually created the PowerPoint.
They hand the CD disc to the AV guy (a really helpful fellow, He copies the CD disc to the hard drive so the "Program runs better." Pops the CD into his pocket and has it burned and puts it back into the laptop when he comes back at break to make sure all is running well.
At the end of the presentation or probably the day he makes a big thing about "erasing" the original from the hard drive for privacy and security but, the dirty deed has already been done.
But if the Republicans still have the disc, then that would get back to the fact that the Democrats are lying about how they got their copy (with all that that implies).