No state in 2012 will be more crucial to Democrats ability to re-take the House than Illinois.

Democrats have a great shot at picking up four seats from Republicans under a new redistricting map drawn by the Democratic legislature, but they will also have to defend the seat of retiring Rep. Jerry Costello (D). In all, as many as six Illinois congressional seats could be competitive come November.

But first come Tuesday’s primaries, which will put the pieces on the board. Our recap of what’s at stake is below:

1. Rep. Adam Kinzinger vs. Rep. Don Manzullo

(16th district Republican primary)

This is the marquee matchup of the day, both because it involves two incumbents and because it looks very competitive. Manzullo is a 10-term member of Congress facing a freshman in a district that is slightly more of Manzullo’s territory than Kinzinger’s.

In this July 28, 2011, file photo, Rep. Adam Kinzinger (R-Ill.) speaks during a news conference on Capitol Hill in Washington. (AP Photo/Harry Hamburg, File)

Given that late surge and a reputation as a strong campaigner, give a slight edge to Kinzinger.

2. Ilya Sheyman vs. Brad Schneider

(10th district Democratic primary)

This primary is a big deal both because it pits a liberal favorite (Sheyman) against a more moderate establishment pick (Schneider) and because it could have big implications for the general election.

Late polling from Sheyman allies (conducted by Public Policy Polling) showed the former community organizer up 45 percent to 27 percent on Schneider. Schneider’s campaign has been put on the defensive, running an ad that plays up his progressive credentials and accuses Sheyman of lying about his record.

The winner gets Rep. Robert Dold (R-Ill.) in a very tough seat for the GOP to hold. But Republicans like their chances a lot better if Sheyman is the nominee.

Fun fact: Sheyman is just 25 years old and a Russian immigrant. If he won a seat, he would likely take the title of youngest congressman from a fellow Illinoisan, Rep. Aaron Schock (R).

3. Rep. Jesse Jackson Jr. vs. former congresswoman Debbie Halvorson

(2nd district Democratic primary)

Don’t expect Jackson to become the next incumbent to fall in a primary. A Lake Research poll conducted for Jackson’s campaign last week shows him leading 59 percent to 23 percent.

The demographics were just too tough for Halvorson here, despite some of Jackson’s personal problems. The district is majority-black, and Jackson leads among African-American voters 69 percent to 15 percent.

4. Tammy Duckworth vs. Raja Krishnamoorthi

(8th district Democratic primary)

Duckworth’s name recognition may have been too much for Krishnamoorthi to overcome. Despite his very strong fundraising, Duckworth remains the strong favorite to face Rep. Joe Walsh (R) in a top targeted seat for Democrats.

If the Iraq veteran can win, Duckworth would get her second shot at winning a congressional seat. In 2006, she lost an open seat to Rep. Peter Roskam (R) — one of relatively few big disappointments for Democrats that year. They’ll be counting on her to win again in 2012.

5. Retiring Rep. Jerry Costello’s (D) seat

(12th district primaries)

This open seat contest has been one of the most meagerly funded major primaries in recent memory. The favorite on the GOP side is 2010 lieutenant governor candidate Jason Plummer, and on the Democratic side, it’s former local school superintendent Brad Harriman, who has Costello’s backing and not much in the way of primary competition.

If anyone has problems Tuesday, it may be Plummer, who has more significant opposition (former Belleville mayor Rodger Cook) and may have hurt himself recently when he accused a pro-life PAC of selling its endorsement to Cook.

This seat, which leans just slightly Democratic, was put in play when Costello unexpectedly retired.

6. Rep. Tim Johnson’s (R) opponent

(13th district Democratic primary)

Greene County State’s Attorney Matt Goetten has the backing of Sen. Dick Durbin (D) and much of the establishment, but as in the 10th district, there is a liberal foil.

His name here is David Gill, an emergency room doctor who’s got a good shot at pulling the upset. As in Schneider’s case, Goetten is running an ad accusing Gill of lying about his record. In this case, a Gill supporter suggested that Goetten’s service in Afghanistan amounted to “probably writing contracts to pay back law school.”

Johnson’s district became much swingier under the new redistricting map, and he also got lots of new territory.

7. The others

In the race to face freshman Rep. Bobby Schilling (R), East Moline Alderwoman Cheri Bustos (D) is a heavy favorite.

And in the race to face Rep. Judy Biggert (R), former congressman Bill Foster (D) should easily win.

Schilling’s and Biggert’s seats, like Dold’s and Walsh’s, are great Democratic pickup opportunities.