So I'm doing a house play through, and this is my fourth run in the game. I've finished Ring a Ding Ding and killed Benny, but when I exit the Tops, Vulpes never showed up to give me the Mark of Caesar and start Render Unto Caesar. So I give Mr House the chip and do a few quests, come back to see if I can find him, and he's nowhere. Used the console to move myself to where he's supposed to be, and it's just an empty spot. Now compared to my other playthroughs, I didn't immediately kill Vulpes in Nipton this time, so apparently he is supposed to be the one who talks to me instead of Alerio. Does anyone know the console command to trigger Vulpes (or Alerio, if that's possible) to start the coversation? Or perhaps someway to trigger the quest without talking to him?

I'm also experiencing this problem. I'd really appreciate any help anyone could provide.

Can you post your savegame (zip or rar file on e. g. mediafire.com) and then I can tell you why he didn't spawn.
If I remember correct guy gets spawned when you haven't "completed" the Legion's fail quest (wrath of caesar).

Oh, well if that's true then I've already failed that. Well thanks for the help, it probably wasn't a bug. I can't speak for Sgt. Lovejoy though.

I believe this is my problem too. Is there any way I could reset Wrath of Caesar and Render unto Caesar so Vulpes will talk to me? Do you still need a save?

Savegame is not needed.
You can try "ResetQuest 00167f0f" in console. This will reset "Wrath of Caesar" Quest with all data which belongs to the quest.
Then "ResetQuest 00129d14" in console. This will reset "Render Unto Caesar" Quest.
If Vulpes isn't dead yet:
00131F78.Enable
0013BF5B.Disable

If Vulpes is dead:
0013A5FF.Enable

In case then still not working when you are at the strip:
00131F78.MoveTo Player 256 256
00131F78.AddScriptPackage VMQ02TalkToPlayer
or for Alerio:
0013A5FF.MoveTo Player 256 256
0013A5FF.AddScriptPackage VMQ02TalkToPlayer

Thanks. All of that is working except for this. It says "Item 'VMQ02TalkToPlayer' not found for Parameter Package. Compiled Script Not Saved!" Is there some reason it doesn't recognize it?

OK, then you have to check the ID for that package in geck.

I don't suppose anyone will still help with this? According to the GECK the ID is VMQ02TalkToPlayer, although if that's the correct script for vulpes, I'm not sure. Shouldn't I be using the setstage command to put Render unto Caesar at the very beginning (I assume Vulpes talking to you is the first stage of that quest.)