Two polls out today for in the Illinois Senate race, both showing a tight race. PPP has Mark Kirk ahead by 4 among likely voters while CNN has Alexi Giannoulias ahead by by 1 among LVs and 4 overall.
PPP (LVs):
Kirk (R) - 40%
Giannoulias (D) - 36%
Jones (Green) - 8%
CNN (LVs):
Giannoulias (D) - 43%
Kirk (R) - 42%
Jones (Green) - 8%
As PPP's Tom Jensen points out, there's a couple of dynamics in the race that could give Giannoulias a boost.
First, supporters of Green Party candidate LeAlan Jones could flip to support Giannoulias as election day approaches and it becomes clear that a vote for Jones is a vote for Kirk. (You could think of their polling preference as a "protest preference" even if they plan to actually vote for Giannoulias.)
Second, the biggest group of undecided voters are Democrats. 46% of undecideds are Dems compared to 27% of GOPers and 27% of Indies. So while Kirk now leads the race by a small margin, with about 1 in 8 voters undecided, Giannoulias stands to gain a disproportionate share of their support which could easily be enough to put him over the top.