Hotels are filled with staff. The staff are usually unionized, and Democratic. Therefore, there is a long list of potential suspects for what you describe.
Here would be the acid test. If the press could find out what "quality" of the presentation the Democrats had, the answer would be clear. Immediately after blockbuster movies appear, pirate editions crop up on tape in the Far East. If the Democrats have the CONTENT of the presentation, but not the QUALITY, then it is clear they did not get a digital copy of the original, but a video copy of the presentation.
The latter answer would point to political spying, so the Washington Post would not touch the story with a ten-foot pole. But the Washington Times could probably get the story.
Congressman Billybob