one client with multiple ssl cert connections to different databases

I setup my postgres servers to allow certificate authentication.  Right now I have two database servers and one application server.  Users are only allowed to connect into the application server, invoke psql, then connect into which ever database server they want.  I have the keys and certs for db server 1 in their .postgresql folder under their home and it works fine, but i can't figure out how to properly setup the environment so that they can connect into either db server with the keys.  I tried to merge the key/cert files in their .postgresql directory with info for both db servers but that didn't work.  I feel like there is an obvious solution to this that I can't see.  Any ideas?