Illinois Democrats picked up four U.S. Congressional seats on Tuesday. In most of those races, redistricting played a role, especially in Chicago’s northern suburbs.

Illinois’ 10th district has a history of sending moderate Republicans — John Porter, Mark Kirk, and most recently Bob Dold — to Washington.

But Dold, the freshman congressman from Kenilworth, lost on Tuesday night to Democratic challenger Brad Schneider. Dold gave a concession speech to a room full of supporters in Lincolnshire.

“We gave it everything we had in this race. We worked hard, made tremendous sacrifices, and didn’t let the daunting odds of redistricting get in our way,” Dold said.

“Daunting” may be the best way to put it, according to David Wasserman, political analyst of the Cook Political Report. Wasserman follows House races across the country and said Dold had a particularly tough road back to Congress after Illinois democrats redrew the map. District maps are redrawn every 10 years to reflect current census data.

“Quantitatively, it was always going to be very difficult for Dold to win his seat that was about 40 percent new to him, and so heavily Democratic,” Wasserman said.

Wasserman said, qualitatively though, Dold probably ran a slightly better campaign. He said Dold ran stronger ads than Schneider did, had more boots on the ground, raised a lot more money, but still lost by about 2,500 votes.

Wasserman says Republican areas like Palatine and Kenilworth in the old 10th district could have made all the difference.

According to Cook County Clerk’s website, Dold carried Palatine precincts by more than 4,000 votes in 2010 when he ran against Democratic candidate Dan Seals, but those precincts were cut out of the 10th district in the new congressional map. Other areas that voted for Dold in 2010, like parts of New Trier township, were also cut out of the district, and new left-leaning areas like Des Plaines and Mundelein were included in the 10th district this election.

“This is what mapmakers are able to do is draw the destiny of districts on the map, and choose voters rather than voters really choosing politicians,” Wasserman said.

Wasserman said other Republican congressmen — like Judy Biggert in the 11th district and Joe Walsh in the 8th district — also felt the effects of redistricting, although to varying degrees. Other factors also played a role in Republican losses, but redistricting was a major one.

Wasserman said if Dold is considering running again in 2014, he might have more luck. He said midterm electorates tend to be older and whiter which may favor Republicans.