While former Massachusetts Gov. Mitt Romney appears poised to win the Illinois GOP presidential primary, several other Republicans will wage much more competitive campaigns Tuesday.

Illinois Democrats overhauled the Congressional map last year, drastically redrawing the district boundaries to create new opportunities for their party to pick up seats. During that redistricting process, Democrats paved the way for a couple of GOP Members to run in the same district.

As a result, Reps. Don Manzullo and Adam Kinzinger are facing off in the Land of Lincoln’s 16th district, the state’s most prominent House primary.

The highly competitive race marks the second time two Members are facing off this cycle and the first set of GOP colleagues to challenge each other.

The race has become a battle of generations and geography, said John McGovern, an Illinois-based Republican consultant.

“The latest polls have shown Congressman Manzullo closing the gap, and so most observers expect it to be a very close race and one determined by geography and turnout,” McGovern said.

Manzullo kicked off the race with a geographical advantage because more of his current district lies in the redrawn 16th district. According to Manzullo’s staff, 47 percent of registered Republican voters in the new 16th district hail from the veteran Congressman’s current district. That’s significantly more than the 25 percent of registered Republican voters that Kinzinger shares between his current district and the redrawn 16th.

Despite this upper hand, many GOP Members initially put money on Kinzinger, a darling of House Republican leadership. House Majority Leader Eric Cantor (Va.) endorsed Kinzinger, and a super PAC run by his former aides spent $50,000 to boost the freshman last week.

The other Republican primary worth watching tonight is in downstate Illinois, where Rep. Jerry Costello’s (D) retirement gives Republicans an opportunity in the marginally Democratic 12th district near St. Louis.

What appeared as a slam-dunk primary for Jason Plummer, the party’s 2010 nominee for lieutenant governor, has proved to be slightly competitive. Plummer is still favored to win tonight thanks to his high name identification from his prior bid, but his fundraising struggled to get off the ground in the first couple of months of the race.

The winner of the GOP primary will likely face former St. Clair County Regional Superintendent of Schools Brad Harriman (D).

On the opposite end of the state in suburban Chicago, two top Democrats are fighting it out for the nomination in the highly competitive 10th district.

The party is seeking to pick up freshman Rep. Robert Dold’s (R) seat in November, but the Democratic frontrunner remained unclear heading into the primary.

Former MoveOn.org organizer Ilya Sheyman galvanized the political left during his campaign. The other top candidate in the primary, businessman Brad Schneider, boasts support from Congressional Democrats, including House Minority Whip Steny Hoyer (Md.).

If Sheyman wins, at least one Democrat expressed trepidation about the 25-year-old being ready to challenge Dold in a targeted race.

“We run the risk of nominating an unqualified and unvetted young activist barely old enough to run and not qualified to serve,” said one Illinois Democratic operative who supports Schneider.

In the western Chicago suburbs, Iraq War veteran Tammy Duckworth (D) is poised to win her primary over former Illinois Deputy Treasurer Raja Krishnamoorthi. Although both candidates ran solid campaigns, Krishnamoorthi struggled to compete with Duckworth’s residual high name identification in the Chicago media market from her high-profile 2006 loss to now-Rep. Peter Roskam.

The victor of the Democratic primary in the 8th district is favored to win the general election over Rep. Joe Walsh this November.

Rep. Jesse Jackson Jr. (D) is also favored to win his primary over former Rep. Debbie Halvorson in the 2nd district. In his toughest re-election race yet, Jackson ran a strong campaign in the redrawn district that spans from southern Chicago to rural Kankakee County.

Further downstate in the 13th district, two Democrats are facing off to challenge Rep. Timothy Johnson in a newly competitive seat.

Johnson is currently viewed as a slight favorite to keep his seat, but House Democrats hope to make the race competitive with Greene County State’s Attorney Matt Goetten.

But Goetten has struggled in the primary against emergency room doctor David Gill. Goetten is still favored to win his party’s nod, but Gill forced Goetten to open up his own wallet during the primary to fuel his campaign with a $50,000 personal donation.

The polls open at 8 a.m. EST and close at 8 p.m. EST.