CHICAGO (AP) - Illinois could be critical to Democrats' hopes of shifting the power balance in the U.S. House, with several competitive races Tuesday that both national parties were watching closely.

Democrats say only two states - New York and California - offer more opportunities for new Democratic districts. In Illinois, they've identified five seats of the 25 that would be needed nationally to regain control of the House.

They're hopeful support for President Barack Obama in his home state will help down-ballot races and that they'll get a boost from a newly-drawn congressional map that carves out Democratic-friendly territories.

However, Republicans are pushing what they believe are say they have strong candidates in those five races and believe they have an edge in another Republican-trending region where a longtime Democratic congressman Jerry Costello in southern Illinois suddenly retired.

Three of the five GOP seats viewed as vulnerable are held by first-term members of Congress.

Both parties have poured millions of dollars into congressional ads and boosted other resources that give Illinois an unusual prominence come Tuesday, given that it's not a swing state and has no high-profile top-of-ticket races.

'We don't get paid too much attention in the presidential election, but there are not many states that have six races that are this close and this interesting - all the different dynamics and different personalities,' said Matt Streb, a political science professor at Northern Illinois University.

Three of those races are in the Chicago area.

One of the most anticipated is the matchup between outspoken tea party Congressman Joe Walsh and Iraq War veteran Tammy Duckworth, who left her Obama administration job to run for Congress. Walsh - whose 2010 win by a slim margin shocked many political experts - ran in the new Democratic-friendly territory to avoid a primary battle with a fellow GOP incumbent.

In recent weeks, the campaign has taken on a spirited - and at times, nasty - tone. During one debate, where roughly 1,000 people showed up and where alcohol was served, drew such loud boos and cheers from the audience that it drowned out the questions.

Walsh has criticized Duckworth, who lost both of her legs in combat, for talking about her military service too much. She shot back with ads that refer to him as 'Deadbeat Joe.' Walsh's ex-wife sued him for more than $100,000 in unpaid child support, an issue he says they cleared up privately.

Democrats also redrew a district in Chicago's northern suburbs to make winning a second term more difficult for first-term Republican Rep. Robert Dold. He faces Democrat Brad Schneider, a businessman. While Dold has outraised Schneider, the district - with a mix of upscale and working-class communities - has been a target of Democrats for years.

A close race also was expected in longtime Republican Rep. Judy Biggert's west suburban Chicago district, much of which is new territory to her. She called the race against former one-term Rep. Bill Foster the most difficult campaign of her life.

Another Republican freshman facing a tough challenge was Bobby Schilling of Colona. Up against Democrat Cheri Bustos, a former East Moline city council member who had an early endorsement from U.S. Sen. Dick Durbin, Schilling has moderated some of the views that earned him strong tea-party support two years ago. The once Democrat-strong district has been redrawn to include more Democratic areas and now extends from the Iowa state line to parts of the Rockford and Peoria areas in central Illinois.

Two unexpected retirements of Illinois congressmen - Republican Tim Johnson and Democrat Jerry Costello - also have created rare openings in downstate Illinois.

Johnson's district, which now stretches from Urbana southwest to Springfield and on to the eastern outskirts of St. Louis' Illinois suburbs, features a matchup between Republican Rodney Davis of Taylorville, a former member of Rep. John Shimkus' staff, and Bloomington physician David Gill, a Democrat.

Republicans hope to wrest Costello's seat away from the Democrats, arguing that the region from the Illinois suburbs of St. Louis to the state's southernmost tip has been turning more conservative for years. Republican lumber executive Jason Plummer faces former Illinois National Guard chief Bill Enyart.

Another race getting attention is the contest in U.S. Rep. Jesse Jackson Jr.'s Chicago-area district.

While he isn't expected to lose the seat he has comfortably held since 1995, Jackson has barely been seen in public for nearly five months while on medical leave for bipolar disorder. Jackson checked into Minnesota's Mayo Clinic for the second time last month.