Sounds like the title to an espionage thriller by John Le Carre......
My thanks go out once again to the fine folks at TVSquad.com. I posted my question about the sixth pall bearer at Leo McGarry's funeral in the episode "Requiem" of 'The West Wing'. And several readers quickly added their two cents.
The head honchos at TVSquad picked up on the question and gave it a showcase to get more responses.
I've since re-watched the scene - several times, in fact, and mostly because I found it very moving, - and I agree with the majority opinion: that the sixth pallbearer is the significant other of Mallory O'Brien, Leo's daughter.
We first see him sitting beside Mallory in the front pew. [Heh heh. "pew".] When the camera cuts to an overhead shot as the pallbearers get into position around Leo's coffin, we see him get out of the front pew to take his place opposite President-elect Santos.
As to who exactly he is, that is, his name, and as to what his relationship with Mallory actually is (husband? fiance? boyfriend? beard?), that seems to be still up in the air and provided plenty of speculation.
Someone claimed that there was a passing line of dialogue early in this season about Mallory on the campaign trail while pregnant. Of course, we're no longer in the 1950s, so that no longer has any bearing on her marital status.
I always hoped she would eventually get back together with Sam Seaborn, but that's life in Toobworld for ya.
Now, if I could just find out who the crying, older woman with reddish hair was in the congregation.... Could that have been Leo's ex-wife, Mallory's mom?