The 11th District is a high priority for the Republican party, which is trying to hang on to the seat, as well as for the Democrats, who are trying to break through.
"As a Democrat I have a great record for business and one that wants to bring common sense to government," said Debbie Halvorson, (D) 11th District candidate.
"I'm concerned our country is going down a path where we're looking too much to government to solve our problem," said Marty Ozinga, (R) 11th District candidate.
A former stay-at-home mom and salesperson, Halvorson has worked up to majority leader. Ozinga has criticized Halvorson for what he says are her close ties to Springfield.
"People see me as a public servant, not a career politician," said Ozinga.
Ozinga comes without any political experience. A conservative and devout Christian, he is the owner of the Ozinga Concrete company, famous for the red and white striped trucks.
"It's a family business. My kids are old enough now to be taking over. But I'm not looking for a fishing boat or a golf course to go to. I like to serve people," Ozinga said.
Because the race has been so tight, there's been a lot of money poured into it. Marty Ozinga has spent $545,000 of his own money as the Democratic national committee has put millions of dollars into the race for Debbie Halvorson.
Halvorson will have her party in Joliet and Ozinga will have his party in Frankfort.
Another marquee race is the rematch in northern Illinois between Kirk, a Naval Reserve commander, and Democrat Dan Seals, a business consultant.
After comfortable margins in elections against other challengers, Kirk beat Seals in 2006 with only 53 percent of the vote in a district with a mix of wealthy and working-class communities that borders Lake Michigan and stretches north of Chicago to almost Wisconsin.
Kirk, a moderate, has played up his contributions to the district, while Seals has portrayed himself as an agent of change like Barack Obama.
The Kirk-Seals race isn't the only congressional rematch. In former GOP House Speaker Dennis Hastert's old district, voters found familiar names on the ballot.
Democrat Rep. Bill Foster snagged Hastert's district when he beat Republican businessman Jim Oberweis of Sugar Grove in a special election earlier this year to replace the retiring Hastert.
If Foster, a physicist from Geneva, wants a new two-year term of his own, he'll have to beat Oberweis again in the 14th District, which stretches from the far-western Chicago suburbs almost to the Mississippi River.
Illinois voters have another open seat to fill with the retirement of longtime GOP Rep. Ray LaHood of Peoria from the 18th District in central Illinois.
Republican Illinois state Rep. Aaron Schock of Peoria could -- at 27 -- become the youngest member of Congress if he beats Democrat Colleen Callahan, a veteran radio broadcaster and Peoria County businesswoman. Green Party candidate Sheldon Schafer of Peoria is also on the ballot.
The Associated Press contributed to this report.