Candidates in six suburban Congressional districts will square off in Tuesday's primary for the right to advance to the November general election.
Democrats will seek their party's nod in the 5th, 6th and 14th districts, while Republicans will do the same in the 9th, 10th and 11th.
Here's a look at some of the choices voters will face:
A seven-person race in the Democratic primary will decide who wages a general election battle with 6th District Republican Rep. Peter Roskam in November.
The candidates have run a largely issues-focused campaign, highlighting opposition to Roskam's views on health care, taxes and the environment. All seven have pledged to support whoever wins the nomination as they try to flip the district blue.
The candidates are Becky Anderson Wilkins, a Naperville bookseller and city council member; Sean Casten, a Downers Grove scientist and entrepreneur; Carole Cheney, a Naperville resident and former congressional aide; Amanda Howland, a Lake Zurich attorney and College of Lake County trustee; Ryan Huffman, a Palatine data analyst; Kelly Mazeski, a Barrington Hills plan commission member and former chemist; and Jennifer Zordani, a Clarendon Hills attorney.
Zordani, 54, says she'll make Washington's laws work for residents' needs.
Mazeski, 58, says she wants to create a Medicare option for all.
Huffman, 31, tells voters he stands for removing the influence of money on politics.
Howland, 65, says she has momentum from drawing 41 percent of the vote against Roskam in 2016, and will fight for progressive values.
Cheney, 57, emphasizes her experience serving constituents locally and accomplishing change nationally.
Casten, 46, calls himself Roskam's "worst nightmare," saying the incumbent can't attack him as a "crazy lefty."
Anderson Wilkins, 60, says she'll stand up for families and will refuse money from lobbyists.
The district forms a "C" that stretches from Tower Lakes to Naperville and covers portions of Cook, DuPage, Kane, Lake and McHenry counties.
Three Democrats are trying to unseat 9-year incumbent Rep. Mike Quigley in what is his first primary challenge for the 5th District seat.
Quigley has risen to national prominence for his position on the House Intelligence Committee, which had been investigating Russian meddling in the 2016 elections.
Of Quigley's three challengers, Benjamin Thomas Wolf has garnered national headlines. The self-described "cannabis candidate" touted his support for marijuana legalization by smoking a joint in a campaign ad. He also caught flak amid accusations of abusive behavior and misrepresenting his background, which he has disputed.
Sameena Mustafa, a commercial real estate tenant advocate, is challenging Quigley's acceptance of campaign contributions from corporations and his votes on defense spending and trade.
Steven Schwartzberg, a former church building and office manager, identifies as a social Democrat and advocates for American Indian tribal sovereignty.
The district covers portions of Rosemont, Des Plaines, Elk Grove Village, Bensenville, Oak Brook and Oakbrook Terrace, as well as Chicago's North Side. The winner will face Republican Tom Hanson of Chicago.
Seven Democrats want to unseat incumbent Republican Rep. Randy Hultgren in the 14th District. The large number of Democrats, pulled from across the seven-county district on the far western fringe of the suburbs, has fueled more attention on a Congressional district viewed as solid Republican territory.
Democrats Matt Brolley, John Hosta, Daniel Roldan-Johnson, Victor Swanson, Lauren Underwood, Jim Walz and George Weber spent most of the past few months seeking ways to differentiate themselves.
Hosta and Walz are the most familiar names. Hosta made an unsuccessful bid to win the Democratic nomination two years ago. Walz was the victor in that contest, but Hultgren bested him by nearly 20 percentage points in the general election.
Healthcare, climate change, immigration, gun control, abortion, financial regulation and campaign finance reform have been the prevailing issues.
Four relatively unknown Republicans are competing for a chance to challenge longtime U.S. Rep. Jan Schakowsky in the 9th Congressional District, which includes parts of the Northwest suburbs, including Arlington Heights, Des Plaines, Mount Prospect, Prospect Heights and Rolling Meadows.
The primary field includes Arlington Heights pastor John Elleson, DePaul University professor and retired Coast Guard member D. Vincent Thomas Jr. of Evanston, retired Army Lt. Col. and think tank director Sargis Sangari of Skokie, and Glencoe resident Max Rice.
Whoever wins faces an uphill climb to defeat Schakowsky, who was elected in 1998. None of the Republican candidates have reported significant fundraising in the heavily Democratic district.
In the 10th Congressional District, three Republicans are running for the chance to battle Democratic incumbent Brad Schneider in November. The hopefuls are Doug Bennett of Deerfield, Dr. Sapan Shah of Libertyville and Jeremy Wynes of Highland Park.
The district includes parts of Lake and Cook counties.
Bennett, a staunch supporter of President Donald Trump, opposes same-sex marriage and abortion rights. Shah and Wynes are painting themselves as social moderates but fiscal conservatives, which better fits the mold of the Republicans who've represented the 10th District in the past.
Shah and Wynes have targeted each other with negative campaign ads, some of which have contained factual inaccuracies. Bennett has been left out of their mudslinging.
Schneider, of Deerfield, is unopposed in the Democratic primary.
Nick Stella and Constant G. "Connor" Vlakancic are running in the 11th District GOP primary for the chance to challenge incumbent Democrat Bill Foster in November.
Stella, 49, is a cardiologist from Darien. Vlakancic, 74, of Aurora, is an importer of Croatian beer, wine and spirits.
Stella narrowly lost a primary bid in 2016, when he tried to earn the Republican Party's nod to challenge Foster. Vlakancic has unsuccessfully sought offices in California and Illinois.
The district covers parts of Cook, DuPage, Kane, Kendall and Will counties, including Aurora, Naperville, Bolingbrook, Burr Ridge and Joliet.
• Daily Herald staff writers James Fuller, Chacour Koop, Russell Lissau, Christopher Placek and Katlyn Smith contributed to this report.