SPRINGFIELD, Ill. • More than a dozen candidates will fight it out in March for the Democratic and Republican nominations to Metro East congressional seats.

Tuesday was Illinois' deadline for candidates to get on the ballot for the March 20 congressional primaries, with the winners squaring off in the November general election. Under newly drawn boundaries, three congressional districts touch the Metro East, including the hotly contested seat of retiring Rep. Jerry Costello, D-Belleville.

Costello, a 22-year veteran of Congress, stunned the Metro East political world in October when he announced he would retire after this term. His 12th District encompasses St. Clair, Monroe and Randolph counties, running along the Missouri border to the southern tip of the state.

It will be the only open seat in Southern Illinois going into the 2012 elections, and one that could be especially contentious because of the shifting demographics of the traditionally Democratic region. Seven candidates — four Republicans and three Democrats — have piled onto the March primary ballots for the seat.

"The area is still leaning Democratic, but the movement has been in the 'red' direction," said John S. Jackson, political scientist at Southern Illinois University Carbondale. "It's definitely competitive."

Still, Jackson noted that the candidates are "virtually unknown," with the arguable exception of Republican Jason Plummer of Fairview Heights, the Metro East lumber company executive who was the 2010 GOP nominee for lieutenant governor.

Vying with him for the nomination will be former Belleville Mayor Rodger Cook, O'Fallon nurse Theresa Kormos and Belleville businesswoman Teri Newman. Newman won the GOP's 2010 primary for the seat, before losing to Costello.

On the Democratic ballot will be Brad Harriman of O'Fallon, a former St. Clair County regional school superintendent who has Costello's backing. Also seeking the Democratic nomination are retired Granite City businessman Kenneth Charles Wiezer and Iraq war veteran Christopher Miller.

The two other congressional seats that converge in the Metro East are the 13th and 15th districts. Both will have Republican incumbents on their primary ballots.

Rep. Tim Johnson, R-Urbana, is considered potentially vulnerable because the 13th District has been reconfigured to take in heavily Democratic areas, including parts of Madison County. In the GOP primary, he will face Madison County veterinarian Michael Firsching and retired ironworker Frank Metzger of Glen Carbon.

The Democratic ballot has drawn two serious contenders: Bloomington physician David Gill, in his fourth attempt against Johnson, and Greene County state's attorney Matt Goetten of Carrollton.

Rep. John Shimkus, R-Collinsville, is unopposed for the GOP nomination to the 15th District. The lone Democrat running is retired nurse Angela Michael of Highland.