How can I ask for someone else's position?

I work at a large company where most people have the same basic position and of course there are managers and assistant managers. There is a "senior" version of the position I am in which requires more effort and skill, teamwork,  is another step towards management, and the compensation is higher. 

I have been with the company for 3 years and have excelled at numerous things, for which I have gotten awards and recognition for from former and my current manager.

The position I'm interested in is still under the same management and with the same group of employees. One of my colleagues currently hold the senior position that I am interested in. His qualifications are that he has been with the company for 5 years and with our current manager for 3 years and his basic sales numbers.

I feel that I am more qualified because the position focuses heavily on teamwork and getting others to perform better. People turn to me for help daily, including my managers. They know that I am reliable and can be counted on to do basically whatever they ask and perform the task quickly and get the job done. The person that currently holds the position is selfish and does not readily help others; he asks for help from almost everyone and turns to me first for help.  He does not do things that do not directly benefit him. He will avoid and stick others with difficult situations so he can focus on easy tasks. 

I do not know how much of these things my manager is directly aware of, but he is smart so I assume he knows. He makes comments under his breath insinuating as much. But as long as this person is successful my manager is, so why would he ruin a good thing?

How do I ask for his position? How do I bring it up to my manager? And how do I ask for his position without directly bashing the other employee? Frankly I do not like him, but obviously I want to keep it professional and focus on my strengths and my qualifications. I feel that if I focus on my strengths, I need to counter them with his shortcomings- how do I avoid this, or is it necessary to avoid this? Should I highlight his shortcomings?

Thanks