I'm on both sides of the argument when it comes to the ending - part of me doesn't appreciate the sudden drop-off after the Ralph commercial, but another part of me doesn't care either. It was either that ending, or one where everything wraps up predictably. Lisa even said it herself - he's too young to run for president, so there's no way he'd make it in without some stupid reason. So, yeah, I can imagine how it would wrap up and I'm not too concerned with the rest of the plot.
But yeah, the pacing wasn't off, but there was just too much to get through in 22 minutes -- it wasn't helped by that couch gag either (even though that was a pretty creative intro). There were a ton of characters going in and out - while that certainly was part of the theme, the focus was going in and out on so many people that the episode really didn't have a sharp focus I believed the episode could have had, so we had Ralph as the episode's frontrunner but we spent more time with the media and then The Simpsons, and then all of the ancillary characters, and then Ralph.
The episode was funny though - and I appreciated the fact that they avoided mostly all the easy jokes (Bill was still in there but one of his jokes was good enough). I loved the Jerkass Homer joke, obviously a nice Nohomers jab if there ever was one. There was another joke aside from the Lenny comment on the political ad that I rolled with, but I can't seem to remember it. Also I liked Marge's jokes in this, and it was a little surprising that she brought up Ralph's past 'relationship' with her.
Overall, the episode was a solid B. I just wish they didn't have to use so many guest stars for these things.
I also noticed a funny change - during the commercial for the episode, the map was almost all red, but during the show it was red, white, and blue in different areas.