A while back a group of architects were trying to decide who in their firm had enough of a relationship with a particular client to make them the right person to lead the response to an RFP. It came down to deciding whether to go with the person who had done a project for that client about 10 years ago or someone who had a friend who might know someone on the selection committee for the project. In my view, we should not have been responding to this RFP because neither of these colleagues had what could reasonably be called a “relationship”.
So what constitutes enough of a relationship to give one enough insight to lead a proposal effort? Here are my baseline criteria:
1) Has met with the prospective decision maker and/or decision makers often enough to know what they like to do for fun, who they like to work with and what are their criteria for a successful working relationship with a consultant like us.
2) Has a track record of interactions with a decision maker that the decision maker would describe as positive.
3) Has communicated enough with that decision maker or those decision makers to know what their key hot button issues are for this particular project and how to support them successfully for this particular pursuit
4) Knows enough about this decision maker to know which of our subconsultants he or she especially likes or dislikes.
If you don’t know at least this much about a potential decision maker for a project, you don’t know them well enough to lead a strategic effort to meet their needs.
aecsarah 
I have a few of close friends who I love dearly and know me like the back of thier hand.
Yet, I would not let any of them perform brain surgery on me.
I see your point. But I think that fact that the client has chosen you in the past outweighs whether you know what they like to do for fun.
Allow me to add this as the new #1 for your list.
* Client has consistantly hired your PM/Lead architect and has given positive reviews of thier work.