What you've written in your submission has got you on the shortlist, but your task is only just beginning when there is a presentation involved.
I was reminded of this when talking to a purchaser recently. After evaluating written responses in a particular tender there was one clear leader, however a presentation formed a significant part of the final score. In this case the person giving the presentation was the company's CEO who obviously decided that his credibility and experience would win the day.
Unfortunately for him, things came unstuck pretty quickly when the first question asked related to a technical component of the bid – and he was unable to give an answer!
The tender was awarded to a smaller competitor.
If a presentation forms a part of an evaluation you can usually assume that it will have a fair influence on the outcome. Make sure you prepare accordingly and not just rely on a Powerpoint version of your written submission.