Rep. Adam Kinzinger speaks at a news conference in July. (Harry Hamburg/AP)

Illinois Democrats, who unabashedly redrew their state’s congressional district lines to boost their chances of picking up seats, claimed their first victim Tuesday as a pair of Republican incumbents waged a fierce battle for their party’s nomination to a single House district outside Chicago.

In a contest pitting tea party activists against the Washington establishment, 10-term Rep. Don Manzullo lost a tough campaign against freshman Rep. Adam Kin­zinger, an Air Force combat pilot who is a favorite of GOP leaders.

The race was a result of Democratic control of levers of power in the state Capitol, something of a rarity after Democrats were wiped out in so many governor and state legislative races in 2010. Illinois Democrats tried to maximize their advantage by drawing a map that would benefit the national party.

Step one of that effort threw Manzullo and Kinzinger into the same district, which wraps around Chicago’s exurbs, stretching from Wisconsin to the north to the Indiana border south of the city. A counterintuitive dynamic emerged in which the insurgents backed the veteran and the establishment got behind the upstart.

With 87 percent of the vote counted, Kinzinger led 56 percent to 44 percent and was declared the winner.

Wary of Kinzinger’s close ties to GOP leaders, several tea party leaders and conservative groups threw their support behind Manzullo, who angrily denounced House Majority Leader Eric Cantor (Va.) for wading into the GOP primary to endorse the freshman.

National Democrats consider Illinois a cornerstone in their effort to gain the 25 House seats in November needed to reclaim the majority, hoping to pick up as many as four seats in the Land of Lincoln in addition to the one they gained by forcing two GOP incumbents into the same district.

Democrats also faced some of their own tough primary battles in a string of ideological and generational challenges, particularly in a district based in Chicago’s South Side. Rep. Jesse L. Jackson Jr. held off former representative Debbie Halvorson, who lost to Kinzinger in 2010 but ran against Jackson when much of her old district ended up in the incumbent’s new 2nd District.

With more than 75 percent of the vote counted, Jackson was well ahead, with 71 percent to Halvorson’s 29 percent.

Jackson’s victory capped off a vigorous campaign in which the son of the famed civil rights leader ran his most aggressive race in years, questioning Halvorson’s support for President Obama’s agenda and her connection to a district that, despite its new configuration, is still more than 50 percent African American.

Trying to become just the second white politician to represent a majority-black district, Halvorson told voters that Jackson had ethical baggage as he remained under investigation by the House ethics committee for an effort by allies to gain him a Senate appointment from then-Gov. Rod Blagojevich (D). The former governor began a 14-year term in federal prison last week after being convicted of corruption related to his efforts to sell the Senate seat.

Halvorson distributed campaign literature showing Jackson with Blagojevich, and accused him of growing complacent and not paying attention to his constituents. “You can’t put your finger on anything Jesse’s done,” she said in an interview while campaigning last week.

In the Chicago suburbs, where Republican freshman Reps. Joe Walsh and Robert Dold are being targeted, Iraq war veteran and former Obama administration official Tammy Duckworth won the Democratic nomination to challenge Walsh, while several activists fought for the right to take on Dold.

Duckworth, who lost her legs when her Black Hawk helicopter was hit by an Iraqi insurgent’s grenade in 2004, became an antiwar icon for liberals in her unsuccessful 2006 bid for a House seat in the western suburbs, raising and spending more than $4 million. In 2009, shortly after Obama’s inauguration, she became an assistant secretary in the Department of Veterans Affairs. She returned to Chicago last year to run in a suburban district that tilted more heavily toward Democrats, seeking to oust one of the most outspoken tea-party-backed House members in Walsh.

Duckworth and Walsh are heroes to the activist bases in their respective parties, and their race is likely to be one of the most expensive House campaigns this fall.

With 60 percent of the vote in, Duckworth led her Democratic rival, businessman Raja Krishnamoorthi, 65 percent to 35 percent.

In the race to take on Dold in the northern suburbs, a pair of Democrats with very different backgrounds fought a close contest, with business consultant Brad Schneider defeating Ilya Sheyman, a community organizer who once worked for the liberal group, 48 percent to 39 percent.