How often and in what ways might internal politics factor into project success?

First according to dictionary.com - Internal politics refers to a set of relationships within an organization which affect the way it works. This kind of relationship is evident in terms of promotions and pay. I see internal politics often playing a role in a projects success. Sometimes because of politics in a workplace you can have someone leading that shouldn't be leading throwing your project under the bus right away. It almost becomes a competition in the workplace and that competition being who can make themselves the most impressive to the boss. Sometimes there isn't even a competition it is just one of the bosses friends that works with you making it even harder to over come. But the politics in a workplace can be a good thing in some cases. The case being the guy that works hardest and has the most respect in the workplace can be at the top of the ladder because he worked the hardest. All in all it does effect the projects in a larger company either in a good light or a bad one is the question of how successful a project becomes.