Lindsay Graham's exclusion from prime time debates prevented him from being a viable presidential candidate, because he did not get to reach a wide enough audience. Additionally, he did not get to show his debate chops against some of the more popular presidential candidates. If he was in a prime time debate, he definitely could have gained more popularity.
I think that if he was included in the presidential debates, maybe he wouldn't have felt the need to drop out of the race entirely. It's sad that he had pressure put upon him to just drop out because he was below 1% of the vote in the current polls.
Lindsay Graham's exclusion from prime time debates prevent him from being a viable Presidential candidate because it prevented the voting pool from being able to understand where he stands on issues. If a candidate does not have representation in context with all of the candidates, they have a much harder time gaining favor with favors, so being excluded from debates prevented Lindsay Graham from getting his message out in comparison with other candidates.
I feel like a majority of the population has absolutely no idea who Lindsay Graham is, and that is because of his lack of exposure. No one knew who Bernie Sanders was until he started to get mainstream media coverage, then people started to pay attention. The same thing could have happened to Lindsay Graham, had he been included.