Well the only polling I have seen shows the race kind of close (about 7%), IMHO the questions were a sort of push poll but that is closer than I would have expected..
There are two other things that I think will result it this being a closer race than I think even the polling shows. I don't think the polling gives the full picture.
The South Asian vote in the district, not sure what the census numbers are, but I think it is safe to say that South Asians make up a larger % of the voters in the 84th than most other districts in the state. I think that is a real advantage for Bansal, I see lots of his yard signs in front of homes I have never seen anyone's yard sign in front of before, (just his sign usually).
Also Aurora had a Indian Festival of Lights event in the district (at Waubonsie Valley HS) with Bansal's campaign being one of the sponsors. From what I understand there was significant crowd at the event, if Kifowit loses this race and it's close, I think that event will have pushed it over the edge since it gave him a lot of exposure for what I suspect was a small investment.
I am not sure there is really much of anything to really drive Democratic turnout in the district (well perhaps the top of the ticket to a limited degree), but don't see a lot of strong Quinn feelings in the district and the county wide races (at least in Kane) don't seem to be generating much heat.
When I got message tested on the race, most of the negative stuff they tested for him involved some tea party stuff, and people who support him also support something you may disagree with. Not sure if that will really get people to the polls.. The 'better' negative stuff seemed to be focused on Kifowit, it was at least more direct.
So I think this is going to be interesting on election night.
Then again I might be nuts...